1------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3------------------------------------------------------------------------------ 4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 5 Bodo Bauer <bb@ricochet.net> 6 72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 9------------------------------------------------------------------------------ 10Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12------------------------------------------------------------------------------ 13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 14 15Table of Contents 16----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 37 score 38 3.2 /proc/<pid>/oom_score - Display current oom-killer score 39 3.3 /proc/<pid>/io - Display the IO accounting fields 40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 41 3.5 /proc/<pid>/mountinfo - Information about mounts 42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 43 3.7 /proc/<pid>/task/<tid>/children - Information about task children 44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 45 3.9 /proc/<pid>/map_files - Information about memory mapped files 46 3.10 /proc/<pid>/timerslack_ns - Task timerslack value 47 3.11 /proc/<pid>/patch_state - Livepatch patch operation state 48 3.12 /proc/<pid>/arch_status - Task architecture specific information 49 50 4 Configuring procfs 51 4.1 Mount options 52 53------------------------------------------------------------------------------ 54Preface 55------------------------------------------------------------------------------ 56 570.1 Introduction/Credits 58------------------------ 59 60This documentation is part of a soon (or so we hope) to be released book on 61the SuSE Linux distribution. As there is no complete documentation for the 62/proc file system and we've used many freely available sources to write these 63chapters, it seems only fair to give the work back to the Linux community. 64This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 65afraid it's still far from complete, but we hope it will be useful. As far as 66we know, it is the first 'all-in-one' document about the /proc file system. It 67is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 68SPARC, AXP, etc., features, you probably won't find what you are looking for. 69It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 70additions and patches are welcome and will be added to this document if you 71mail them to Bodo. 72 73We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 74other people for help compiling this documentation. We'd also like to extend a 75special thank you to Andi Kleen for documentation, which we relied on heavily 76to create this document, as well as the additional information he provided. 77Thanks to everybody else who contributed source or docs to the Linux kernel 78and helped create a great piece of software... :) 79 80If you have any comments, corrections or additions, please don't hesitate to 81contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 82document. 83 84The latest version of this document is available online at 85http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 86 87If the above direction does not works for you, you could try the kernel 88mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 89comandante@zaralinux.com. 90 910.2 Legal Stuff 92--------------- 93 94We don't guarantee the correctness of this document, and if you come to us 95complaining about how you screwed up your system because of incorrect 96documentation, we won't feel responsible... 97 98------------------------------------------------------------------------------ 99CHAPTER 1: COLLECTING SYSTEM INFORMATION 100------------------------------------------------------------------------------ 101 102------------------------------------------------------------------------------ 103In This Chapter 104------------------------------------------------------------------------------ 105* Investigating the properties of the pseudo file system /proc and its 106 ability to provide information on the running Linux system 107* Examining /proc's structure 108* Uncovering various information about the kernel and the processes running 109 on the system 110------------------------------------------------------------------------------ 111 112 113The proc file system acts as an interface to internal data structures in the 114kernel. It can be used to obtain information about the system and to change 115certain kernel parameters at runtime (sysctl). 116 117First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 118show you how you can use /proc/sys to change settings. 119 1201.1 Process-Specific Subdirectories 121----------------------------------- 122 123The directory /proc contains (among other things) one subdirectory for each 124process running on the system, which is named after the process ID (PID). 125 126The link self points to the process reading the file system. Each process 127subdirectory has the entries listed in Table 1-1. 128 129Note that an open a file descriptor to /proc/<pid> or to any of its 130contained files or subdirectories does not prevent <pid> being reused 131for some other process in the event that <pid> exits. Operations on 132open /proc/<pid> file descriptors corresponding to dead processes 133never act on any new process that the kernel may, through chance, have 134also assigned the process ID <pid>. Instead, operations on these FDs 135usually fail with ESRCH. 136 137Table 1-1: Process specific entries in /proc 138.............................................................................. 139 File Content 140 clear_refs Clears page referenced bits shown in smaps output 141 cmdline Command line arguments 142 cpu Current and last cpu in which it was executed (2.4)(smp) 143 cwd Link to the current working directory 144 environ Values of environment variables 145 exe Link to the executable of this process 146 fd Directory, which contains all file descriptors 147 maps Memory maps to executables and library files (2.4) 148 mem Memory held by this process 149 root Link to the root directory of this process 150 stat Process status 151 statm Process memory status information 152 status Process status in human readable form 153 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function 154 symbol the task is blocked in - or "0" if not blocked. 155 pagemap Page table 156 stack Report full stack trace, enable via CONFIG_STACKTRACE 157 smaps An extension based on maps, showing the memory consumption of 158 each mapping and flags associated with it 159 smaps_rollup Accumulated smaps stats for all mappings of the process. This 160 can be derived from smaps, but is faster and more convenient 161 numa_maps An extension based on maps, showing the memory locality and 162 binding policy as well as mem usage (in pages) of each mapping. 163.............................................................................. 164 165For example, to get the status information of a process, all you have to do is 166read the file /proc/PID/status: 167 168 >cat /proc/self/status 169 Name: cat 170 State: R (running) 171 Tgid: 5452 172 Pid: 5452 173 PPid: 743 174 TracerPid: 0 (2.4) 175 Uid: 501 501 501 501 176 Gid: 100 100 100 100 177 FDSize: 256 178 Groups: 100 14 16 179 VmPeak: 5004 kB 180 VmSize: 5004 kB 181 VmLck: 0 kB 182 VmHWM: 476 kB 183 VmRSS: 476 kB 184 RssAnon: 352 kB 185 RssFile: 120 kB 186 RssShmem: 4 kB 187 VmData: 156 kB 188 VmStk: 88 kB 189 VmExe: 68 kB 190 VmLib: 1412 kB 191 VmPTE: 20 kb 192 VmSwap: 0 kB 193 HugetlbPages: 0 kB 194 CoreDumping: 0 195 THP_enabled: 1 196 Threads: 1 197 SigQ: 0/28578 198 SigPnd: 0000000000000000 199 ShdPnd: 0000000000000000 200 SigBlk: 0000000000000000 201 SigIgn: 0000000000000000 202 SigCgt: 0000000000000000 203 CapInh: 00000000fffffeff 204 CapPrm: 0000000000000000 205 CapEff: 0000000000000000 206 CapBnd: ffffffffffffffff 207 CapAmb: 0000000000000000 208 NoNewPrivs: 0 209 Seccomp: 0 210 Speculation_Store_Bypass: thread vulnerable 211 voluntary_ctxt_switches: 0 212 nonvoluntary_ctxt_switches: 1 213 214This shows you nearly the same information you would get if you viewed it with 215the ps command. In fact, ps uses the proc file system to obtain its 216information. But you get a more detailed view of the process by reading the 217file /proc/PID/status. It fields are described in table 1-2. 218 219The statm file contains more detailed information about the process 220memory usage. Its seven fields are explained in Table 1-3. The stat file 221contains details information about the process itself. Its fields are 222explained in Table 1-4. 223 224(for SMP CONFIG users) 225For making accounting scalable, RSS related information are handled in an 226asynchronous manner and the value may not be very precise. To see a precise 227snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 228It's slow but very precise. 229 230Table 1-2: Contents of the status files (as of 4.19) 231.............................................................................. 232 Field Content 233 Name filename of the executable 234 Umask file mode creation mask 235 State state (R is running, S is sleeping, D is sleeping 236 in an uninterruptible wait, Z is zombie, 237 T is traced or stopped) 238 Tgid thread group ID 239 Ngid NUMA group ID (0 if none) 240 Pid process id 241 PPid process id of the parent process 242 TracerPid PID of process tracing this process (0 if not) 243 Uid Real, effective, saved set, and file system UIDs 244 Gid Real, effective, saved set, and file system GIDs 245 FDSize number of file descriptor slots currently allocated 246 Groups supplementary group list 247 NStgid descendant namespace thread group ID hierarchy 248 NSpid descendant namespace process ID hierarchy 249 NSpgid descendant namespace process group ID hierarchy 250 NSsid descendant namespace session ID hierarchy 251 VmPeak peak virtual memory size 252 VmSize total program size 253 VmLck locked memory size 254 VmPin pinned memory size 255 VmHWM peak resident set size ("high water mark") 256 VmRSS size of memory portions. It contains the three 257 following parts (VmRSS = RssAnon + RssFile + RssShmem) 258 RssAnon size of resident anonymous memory 259 RssFile size of resident file mappings 260 RssShmem size of resident shmem memory (includes SysV shm, 261 mapping of tmpfs and shared anonymous mappings) 262 VmData size of private data segments 263 VmStk size of stack segments 264 VmExe size of text segment 265 VmLib size of shared library code 266 VmPTE size of page table entries 267 VmSwap amount of swap used by anonymous private data 268 (shmem swap usage is not included) 269 HugetlbPages size of hugetlb memory portions 270 CoreDumping process's memory is currently being dumped 271 (killing the process may lead to a corrupted core) 272 THP_enabled process is allowed to use THP (returns 0 when 273 PR_SET_THP_DISABLE is set on the process 274 Threads number of threads 275 SigQ number of signals queued/max. number for queue 276 SigPnd bitmap of pending signals for the thread 277 ShdPnd bitmap of shared pending signals for the process 278 SigBlk bitmap of blocked signals 279 SigIgn bitmap of ignored signals 280 SigCgt bitmap of caught signals 281 CapInh bitmap of inheritable capabilities 282 CapPrm bitmap of permitted capabilities 283 CapEff bitmap of effective capabilities 284 CapBnd bitmap of capabilities bounding set 285 CapAmb bitmap of ambient capabilities 286 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...) 287 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) 288 Speculation_Store_Bypass speculative store bypass mitigation status 289 Cpus_allowed mask of CPUs on which this process may run 290 Cpus_allowed_list Same as previous, but in "list format" 291 Mems_allowed mask of memory nodes allowed to this process 292 Mems_allowed_list Same as previous, but in "list format" 293 voluntary_ctxt_switches number of voluntary context switches 294 nonvoluntary_ctxt_switches number of non voluntary context switches 295.............................................................................. 296 297Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 298.............................................................................. 299 Field Content 300 size total program size (pages) (same as VmSize in status) 301 resident size of memory portions (pages) (same as VmRSS in status) 302 shared number of pages that are shared (i.e. backed by a file, same 303 as RssFile+RssShmem in status) 304 trs number of pages that are 'code' (not including libs; broken, 305 includes data segment) 306 lrs number of pages of library (always 0 on 2.6) 307 drs number of pages of data/stack (including libs; broken, 308 includes library text) 309 dt number of dirty pages (always 0 on 2.6) 310.............................................................................. 311 312 313Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 314.............................................................................. 315 Field Content 316 pid process id 317 tcomm filename of the executable 318 state state (R is running, S is sleeping, D is sleeping in an 319 uninterruptible wait, Z is zombie, T is traced or stopped) 320 ppid process id of the parent process 321 pgrp pgrp of the process 322 sid session id 323 tty_nr tty the process uses 324 tty_pgrp pgrp of the tty 325 flags task flags 326 min_flt number of minor faults 327 cmin_flt number of minor faults with child's 328 maj_flt number of major faults 329 cmaj_flt number of major faults with child's 330 utime user mode jiffies 331 stime kernel mode jiffies 332 cutime user mode jiffies with child's 333 cstime kernel mode jiffies with child's 334 priority priority level 335 nice nice level 336 num_threads number of threads 337 it_real_value (obsolete, always 0) 338 start_time time the process started after system boot 339 vsize virtual memory size 340 rss resident set memory size 341 rsslim current limit in bytes on the rss 342 start_code address above which program text can run 343 end_code address below which program text can run 344 start_stack address of the start of the main process stack 345 esp current value of ESP 346 eip current value of EIP 347 pending bitmap of pending signals 348 blocked bitmap of blocked signals 349 sigign bitmap of ignored signals 350 sigcatch bitmap of caught signals 351 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead) 352 0 (place holder) 353 0 (place holder) 354 exit_signal signal to send to parent thread on exit 355 task_cpu which CPU the task is scheduled on 356 rt_priority realtime priority 357 policy scheduling policy (man sched_setscheduler) 358 blkio_ticks time spent waiting for block IO 359 gtime guest time of the task in jiffies 360 cgtime guest time of the task children in jiffies 361 start_data address above which program data+bss is placed 362 end_data address below which program data+bss is placed 363 start_brk address above which program heap can be expanded with brk() 364 arg_start address above which program command line is placed 365 arg_end address below which program command line is placed 366 env_start address above which program environment is placed 367 env_end address below which program environment is placed 368 exit_code the thread's exit_code in the form reported by the waitpid system call 369.............................................................................. 370 371The /proc/PID/maps file contains the currently mapped memory regions and 372their access permissions. 373 374The format is: 375 376address perms offset dev inode pathname 377 37808048000-08049000 r-xp 00000000 03:00 8312 /opt/test 37908049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3800804a000-0806b000 rw-p 00000000 00:00 0 [heap] 381a7cb1000-a7cb2000 ---p 00000000 00:00 0 382a7cb2000-a7eb2000 rw-p 00000000 00:00 0 383a7eb2000-a7eb3000 ---p 00000000 00:00 0 384a7eb3000-a7ed5000 rw-p 00000000 00:00 0 385a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 386a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 387a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 388a800b000-a800e000 rw-p 00000000 00:00 0 389a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 390a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 391a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 392a8024000-a8027000 rw-p 00000000 00:00 0 393a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 394a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 395a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 396aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 397ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 398 399where "address" is the address space in the process that it occupies, "perms" 400is a set of permissions: 401 402 r = read 403 w = write 404 x = execute 405 s = shared 406 p = private (copy on write) 407 408"offset" is the offset into the mapping, "dev" is the device (major:minor), and 409"inode" is the inode on that device. 0 indicates that no inode is associated 410with the memory region, as the case would be with BSS (uninitialized data). 411The "pathname" shows the name associated file for this mapping. If the mapping 412is not associated with a file: 413 414 [heap] = the heap of the program 415 [stack] = the stack of the main process 416 [vdso] = the "virtual dynamic shared object", 417 the kernel system call handler 418 419 or if empty, the mapping is anonymous. 420 421The /proc/PID/smaps is an extension based on maps, showing the memory 422consumption for each of the process's mappings. For each mapping (aka Virtual 423Memory Area, or VMA) there is a series of lines such as the following: 424 42508048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 426 427Size: 1084 kB 428KernelPageSize: 4 kB 429MMUPageSize: 4 kB 430Rss: 892 kB 431Pss: 374 kB 432Shared_Clean: 892 kB 433Shared_Dirty: 0 kB 434Private_Clean: 0 kB 435Private_Dirty: 0 kB 436Referenced: 892 kB 437Anonymous: 0 kB 438LazyFree: 0 kB 439AnonHugePages: 0 kB 440ShmemPmdMapped: 0 kB 441Shared_Hugetlb: 0 kB 442Private_Hugetlb: 0 kB 443Swap: 0 kB 444SwapPss: 0 kB 445KernelPageSize: 4 kB 446MMUPageSize: 4 kB 447Locked: 0 kB 448THPeligible: 0 449VmFlags: rd ex mr mw me dw 450 451The first of these lines shows the same information as is displayed for the 452mapping in /proc/PID/maps. Following lines show the size of the mapping 453(size); the size of each page allocated when backing a VMA (KernelPageSize), 454which is usually the same as the size in the page table entries; the page size 455used by the MMU when backing a VMA (in most cases, the same as KernelPageSize); 456the amount of the mapping that is currently resident in RAM (RSS); the 457process' proportional share of this mapping (PSS); and the number of clean and 458dirty shared and private pages in the mapping. 459 460The "proportional set size" (PSS) of a process is the count of pages it has 461in memory, where each page is divided by the number of processes sharing it. 462So if a process has 1000 pages all to itself, and 1000 shared with one other 463process, its PSS will be 1500. 464Note that even a page which is part of a MAP_SHARED mapping, but has only 465a single pte mapped, i.e. is currently used by only one process, is accounted 466as private and not as shared. 467"Referenced" indicates the amount of memory currently marked as referenced or 468accessed. 469"Anonymous" shows the amount of memory that does not belong to any file. Even 470a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 471and a page is modified, the file page is replaced by a private anonymous copy. 472"LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE). 473The memory isn't freed immediately with madvise(). It's freed in memory 474pressure if the memory is clean. Please note that the printed value might 475be lower than the real value due to optimizations used in the current 476implementation. If this is not desirable please file a bug report. 477"AnonHugePages" shows the ammount of memory backed by transparent hugepage. 478"ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by 479huge pages. 480"Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by 481hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical 482reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field. 483"Swap" shows how much would-be-anonymous memory is also used, but out on swap. 484For shmem mappings, "Swap" includes also the size of the mapped (and not 485replaced by copy-on-write) part of the underlying shmem object out on swap. 486"SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this 487does not take into account swapped out page of underlying shmem objects. 488"Locked" indicates whether the mapping is locked in memory or not. 489"THPeligible" indicates whether the mapping is eligible for allocating THP 490pages - 1 if true, 0 otherwise. It just shows the current status. 491 492"VmFlags" field deserves a separate description. This member represents the kernel 493flags associated with the particular virtual memory area in two letter encoded 494manner. The codes are the following: 495 rd - readable 496 wr - writeable 497 ex - executable 498 sh - shared 499 mr - may read 500 mw - may write 501 me - may execute 502 ms - may share 503 gd - stack segment growns down 504 pf - pure PFN range 505 dw - disabled write to the mapped file 506 lo - pages are locked in memory 507 io - memory mapped I/O area 508 sr - sequential read advise provided 509 rr - random read advise provided 510 dc - do not copy area on fork 511 de - do not expand area on remapping 512 ac - area is accountable 513 nr - swap space is not reserved for the area 514 ht - area uses huge tlb pages 515 ar - architecture specific flag 516 dd - do not include area into core dump 517 sd - soft-dirty flag 518 mm - mixed map area 519 hg - huge page advise flag 520 nh - no-huge page advise flag 521 mg - mergable advise flag 522 523Note that there is no guarantee that every flag and associated mnemonic will 524be present in all further kernel releases. Things get changed, the flags may 525be vanished or the reverse -- new added. Interpretation of their meaning 526might change in future as well. So each consumer of these flags has to 527follow each specific kernel version for the exact semantic. 528 529This file is only present if the CONFIG_MMU kernel configuration option is 530enabled. 531 532Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent 533output can be achieved only in the single read call). 534This typically manifests when doing partial reads of these files while the 535memory map is being modified. Despite the races, we do provide the following 536guarantees: 537 5381) The mapped addresses never go backwards, which implies no two 539 regions will ever overlap. 5402) If there is something at a given vaddr during the entirety of the 541 life of the smaps/maps walk, there will be some output for it. 542 543The /proc/PID/smaps_rollup file includes the same fields as /proc/PID/smaps, 544but their values are the sums of the corresponding values for all mappings of 545the process. Additionally, it contains these fields: 546 547Pss_Anon 548Pss_File 549Pss_Shmem 550 551They represent the proportional shares of anonymous, file, and shmem pages, as 552described for smaps above. These fields are omitted in smaps since each 553mapping identifies the type (anon, file, or shmem) of all pages it contains. 554Thus all information in smaps_rollup can be derived from smaps, but at a 555significantly higher cost. 556 557The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 558bits on both physical and virtual pages associated with a process, and the 559soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst 560for details). 561To clear the bits for all the pages associated with the process 562 > echo 1 > /proc/PID/clear_refs 563 564To clear the bits for the anonymous pages associated with the process 565 > echo 2 > /proc/PID/clear_refs 566 567To clear the bits for the file mapped pages associated with the process 568 > echo 3 > /proc/PID/clear_refs 569 570To clear the soft-dirty bit 571 > echo 4 > /proc/PID/clear_refs 572 573To reset the peak resident set size ("high water mark") to the process's 574current value: 575 > echo 5 > /proc/PID/clear_refs 576 577Any other value written to /proc/PID/clear_refs will have no effect. 578 579The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 580using /proc/kpageflags and number of times a page is mapped using 581/proc/kpagecount. For detailed explanation, see 582Documentation/admin-guide/mm/pagemap.rst. 583 584The /proc/pid/numa_maps is an extension based on maps, showing the memory 585locality and binding policy, as well as the memory usage (in pages) of 586each mapping. The output follows a general format where mapping details get 587summarized separated by blank spaces, one mapping per each file line: 588 589address policy mapping details 590 59100400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4 59200600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5933206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4 594320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5953206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5963206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4 5973206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4 598320698b000 default file=/lib64/libc-2.12.so 5993206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4 6003206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4 6013206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4 6027f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4 6037f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4 6047f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048 6057fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4 6067fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4 607 608Where: 609"address" is the starting address for the mapping; 610"policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst); 611"mapping details" summarizes mapping data such as mapping type, page usage counters, 612node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page 613size, in KB, that is backing the mapping up. 614 6151.2 Kernel data 616--------------- 617 618Similar to the process entries, the kernel data files give information about 619the running kernel. The files used to obtain this information are contained in 620/proc and are listed in Table 1-5. Not all of these will be present in your 621system. It depends on the kernel configuration and the loaded modules, which 622files are there, and which are missing. 623 624Table 1-5: Kernel info in /proc 625.............................................................................. 626 File Content 627 apm Advanced power management info 628 buddyinfo Kernel memory allocator information (see text) (2.5) 629 bus Directory containing bus specific information 630 cmdline Kernel command line 631 cpuinfo Info about the CPU 632 devices Available devices (block and character) 633 dma Used DMS channels 634 filesystems Supported filesystems 635 driver Various drivers grouped here, currently rtc (2.4) 636 execdomains Execdomains, related to security (2.4) 637 fb Frame Buffer devices (2.4) 638 fs File system parameters, currently nfs/exports (2.4) 639 ide Directory containing info about the IDE subsystem 640 interrupts Interrupt usage 641 iomem Memory map (2.4) 642 ioports I/O port usage 643 irq Masks for irq to cpu affinity (2.4)(smp?) 644 isapnp ISA PnP (Plug&Play) Info (2.4) 645 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 646 kmsg Kernel messages 647 ksyms Kernel symbol table 648 loadavg Load average of last 1, 5 & 15 minutes 649 locks Kernel locks 650 meminfo Memory info 651 misc Miscellaneous 652 modules List of loaded modules 653 mounts Mounted filesystems 654 net Networking info (see text) 655 pagetypeinfo Additional page allocator information (see text) (2.5) 656 partitions Table of partitions known to the system 657 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 658 decoupled by lspci (2.4) 659 rtc Real time clock 660 scsi SCSI info (see text) 661 slabinfo Slab pool info 662 softirqs softirq usage 663 stat Overall statistics 664 swaps Swap space utilization 665 sys See chapter 2 666 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 667 tty Info of tty drivers 668 uptime Wall clock since boot, combined idle time of all cpus 669 version Kernel version 670 video bttv info of video resources (2.4) 671 vmallocinfo Show vmalloced areas 672.............................................................................. 673 674You can, for example, check which interrupts are currently in use and what 675they are used for by looking in the file /proc/interrupts: 676 677 > cat /proc/interrupts 678 CPU0 679 0: 8728810 XT-PIC timer 680 1: 895 XT-PIC keyboard 681 2: 0 XT-PIC cascade 682 3: 531695 XT-PIC aha152x 683 4: 2014133 XT-PIC serial 684 5: 44401 XT-PIC pcnet_cs 685 8: 2 XT-PIC rtc 686 11: 8 XT-PIC i82365 687 12: 182918 XT-PIC PS/2 Mouse 688 13: 1 XT-PIC fpu 689 14: 1232265 XT-PIC ide0 690 15: 7 XT-PIC ide1 691 NMI: 0 692 693In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 694output of a SMP machine): 695 696 > cat /proc/interrupts 697 698 CPU0 CPU1 699 0: 1243498 1214548 IO-APIC-edge timer 700 1: 8949 8958 IO-APIC-edge keyboard 701 2: 0 0 XT-PIC cascade 702 5: 11286 10161 IO-APIC-edge soundblaster 703 8: 1 0 IO-APIC-edge rtc 704 9: 27422 27407 IO-APIC-edge 3c503 705 12: 113645 113873 IO-APIC-edge PS/2 Mouse 706 13: 0 0 XT-PIC fpu 707 14: 22491 24012 IO-APIC-edge ide0 708 15: 2183 2415 IO-APIC-edge ide1 709 17: 30564 30414 IO-APIC-level eth0 710 18: 177 164 IO-APIC-level bttv 711 NMI: 2457961 2457959 712 LOC: 2457882 2457881 713 ERR: 2155 714 715NMI is incremented in this case because every timer interrupt generates a NMI 716(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 717 718LOC is the local interrupt counter of the internal APIC of every CPU. 719 720ERR is incremented in the case of errors in the IO-APIC bus (the bus that 721connects the CPUs in a SMP system. This means that an error has been detected, 722the IO-APIC automatically retry the transmission, so it should not be a big 723problem, but you should read the SMP-FAQ. 724 725In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 726/proc/interrupts to display every IRQ vector in use by the system, not 727just those considered 'most important'. The new vectors are: 728 729 THR -- interrupt raised when a machine check threshold counter 730 (typically counting ECC corrected errors of memory or cache) exceeds 731 a configurable threshold. Only available on some systems. 732 733 TRM -- a thermal event interrupt occurs when a temperature threshold 734 has been exceeded for the CPU. This interrupt may also be generated 735 when the temperature drops back to normal. 736 737 SPU -- a spurious interrupt is some interrupt that was raised then lowered 738 by some IO device before it could be fully processed by the APIC. Hence 739 the APIC sees the interrupt but does not know what device it came from. 740 For this case the APIC will generate the interrupt with a IRQ vector 741 of 0xff. This might also be generated by chipset bugs. 742 743 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 744 sent from one CPU to another per the needs of the OS. Typically, 745 their statistics are used by kernel developers and interested users to 746 determine the occurrence of interrupts of the given type. 747 748The above IRQ vectors are displayed only when relevant. For example, 749the threshold vector does not exist on x86_64 platforms. Others are 750suppressed when the system is a uniprocessor. As of this writing, only 751i386 and x86_64 platforms support the new IRQ vector displays. 752 753Of some interest is the introduction of the /proc/irq directory to 2.4. 754It could be used to set IRQ to CPU affinity, this means that you can "hook" an 755IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 756irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 757prof_cpu_mask. 758 759For example 760 > ls /proc/irq/ 761 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 762 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 763 > ls /proc/irq/0/ 764 smp_affinity 765 766smp_affinity is a bitmask, in which you can specify which CPUs can handle the 767IRQ, you can set it by doing: 768 769 > echo 1 > /proc/irq/10/smp_affinity 770 771This means that only the first CPU will handle the IRQ, but you can also echo 7725 which means that only the first and third CPU can handle the IRQ. 773 774The contents of each smp_affinity file is the same by default: 775 776 > cat /proc/irq/0/smp_affinity 777 ffffffff 778 779There is an alternate interface, smp_affinity_list which allows specifying 780a cpu range instead of a bitmask: 781 782 > cat /proc/irq/0/smp_affinity_list 783 1024-1031 784 785The default_smp_affinity mask applies to all non-active IRQs, which are the 786IRQs which have not yet been allocated/activated, and hence which lack a 787/proc/irq/[0-9]* directory. 788 789The node file on an SMP system shows the node to which the device using the IRQ 790reports itself as being attached. This hardware locality information does not 791include information about any possible driver locality preference. 792 793prof_cpu_mask specifies which CPUs are to be profiled by the system wide 794profiler. Default value is ffffffff (all cpus if there are only 32 of them). 795 796The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 797between all the CPUs which are allowed to handle it. As usual the kernel has 798more info than you and does a better job than you, so the defaults are the 799best choice for almost everyone. [Note this applies only to those IO-APIC's 800that support "Round Robin" interrupt distribution.] 801 802There are three more important subdirectories in /proc: net, scsi, and sys. 803The general rule is that the contents, or even the existence of these 804directories, depend on your kernel configuration. If SCSI is not enabled, the 805directory scsi may not exist. The same is true with the net, which is there 806only when networking support is present in the running kernel. 807 808The slabinfo file gives information about memory usage at the slab level. 809Linux uses slab pools for memory management above page level in version 2.2. 810Commonly used objects have their own slab pool (such as network buffers, 811directory cache, and so on). 812 813.............................................................................. 814 815> cat /proc/buddyinfo 816 817Node 0, zone DMA 0 4 5 4 4 3 ... 818Node 0, zone Normal 1 0 0 1 101 8 ... 819Node 0, zone HighMem 2 0 0 1 1 0 ... 820 821External fragmentation is a problem under some workloads, and buddyinfo is a 822useful tool for helping diagnose these problems. Buddyinfo will give you a 823clue as to how big an area you can safely allocate, or why a previous 824allocation failed. 825 826Each column represents the number of pages of a certain order which are 827available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 828ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 829available in ZONE_NORMAL, etc... 830 831More information relevant to external fragmentation can be found in 832pagetypeinfo. 833 834> cat /proc/pagetypeinfo 835Page block order: 9 836Pages per block: 512 837 838Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 839Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 840Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 841Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 842Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 843Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 844Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 845Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 846Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 847Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 848Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 849 850Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 851Node 0, zone DMA 2 0 5 1 0 852Node 0, zone DMA32 41 6 967 2 0 853 854Fragmentation avoidance in the kernel works by grouping pages of different 855migrate types into the same contiguous regions of memory called page blocks. 856A page block is typically the size of the default hugepage size e.g. 2MB on 857X86-64. By keeping pages grouped based on their ability to move, the kernel 858can reclaim pages within a page block to satisfy a high-order allocation. 859 860The pagetypinfo begins with information on the size of a page block. It 861then gives the same type of information as buddyinfo except broken down 862by migrate-type and finishes with details on how many page blocks of each 863type exist. 864 865If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 866from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can 867make an estimate of the likely number of huge pages that can be allocated 868at a given point in time. All the "Movable" blocks should be allocatable 869unless memory has been mlock()'d. Some of the Reclaimable blocks should 870also be allocatable although a lot of filesystem metadata may have to be 871reclaimed to achieve this. 872 873.............................................................................. 874 875meminfo: 876 877Provides information about distribution and utilization of memory. This 878varies by architecture and compile options. The following is from a 87916GB PIII, which has highmem enabled. You may not have all of these fields. 880 881> cat /proc/meminfo 882 883MemTotal: 16344972 kB 884MemFree: 13634064 kB 885MemAvailable: 14836172 kB 886Buffers: 3656 kB 887Cached: 1195708 kB 888SwapCached: 0 kB 889Active: 891636 kB 890Inactive: 1077224 kB 891HighTotal: 15597528 kB 892HighFree: 13629632 kB 893LowTotal: 747444 kB 894LowFree: 4432 kB 895SwapTotal: 0 kB 896SwapFree: 0 kB 897Dirty: 968 kB 898Writeback: 0 kB 899AnonPages: 861800 kB 900Mapped: 280372 kB 901Shmem: 644 kB 902KReclaimable: 168048 kB 903Slab: 284364 kB 904SReclaimable: 159856 kB 905SUnreclaim: 124508 kB 906PageTables: 24448 kB 907NFS_Unstable: 0 kB 908Bounce: 0 kB 909WritebackTmp: 0 kB 910CommitLimit: 7669796 kB 911Committed_AS: 100056 kB 912VmallocTotal: 112216 kB 913VmallocUsed: 428 kB 914VmallocChunk: 111088 kB 915Percpu: 62080 kB 916HardwareCorrupted: 0 kB 917AnonHugePages: 49152 kB 918ShmemHugePages: 0 kB 919ShmemPmdMapped: 0 kB 920 921 922 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 923 bits and the kernel binary code) 924 MemFree: The sum of LowFree+HighFree 925MemAvailable: An estimate of how much memory is available for starting new 926 applications, without swapping. Calculated from MemFree, 927 SReclaimable, the size of the file LRU lists, and the low 928 watermarks in each zone. 929 The estimate takes into account that the system needs some 930 page cache to function well, and that not all reclaimable 931 slab will be reclaimable, due to items being in use. The 932 impact of those factors will vary from system to system. 933 Buffers: Relatively temporary storage for raw disk blocks 934 shouldn't get tremendously large (20MB or so) 935 Cached: in-memory cache for files read from the disk (the 936 pagecache). Doesn't include SwapCached 937 SwapCached: Memory that once was swapped out, is swapped back in but 938 still also is in the swapfile (if memory is needed it 939 doesn't need to be swapped out AGAIN because it is already 940 in the swapfile. This saves I/O) 941 Active: Memory that has been used more recently and usually not 942 reclaimed unless absolutely necessary. 943 Inactive: Memory which has been less recently used. It is more 944 eligible to be reclaimed for other purposes 945 HighTotal: 946 HighFree: Highmem is all memory above ~860MB of physical memory 947 Highmem areas are for use by userspace programs, or 948 for the pagecache. The kernel must use tricks to access 949 this memory, making it slower to access than lowmem. 950 LowTotal: 951 LowFree: Lowmem is memory which can be used for everything that 952 highmem can be used for, but it is also available for the 953 kernel's use for its own data structures. Among many 954 other things, it is where everything from the Slab is 955 allocated. Bad things happen when you're out of lowmem. 956 SwapTotal: total amount of swap space available 957 SwapFree: Memory which has been evicted from RAM, and is temporarily 958 on the disk 959 Dirty: Memory which is waiting to get written back to the disk 960 Writeback: Memory which is actively being written back to the disk 961 AnonPages: Non-file backed pages mapped into userspace page tables 962HardwareCorrupted: The amount of RAM/memory in KB, the kernel identifies as 963 corrupted. 964AnonHugePages: Non-file backed huge pages mapped into userspace page tables 965 Mapped: files which have been mmaped, such as libraries 966 Shmem: Total memory used by shared memory (shmem) and tmpfs 967ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated 968 with huge pages 969ShmemPmdMapped: Shared memory mapped into userspace with huge pages 970KReclaimable: Kernel allocations that the kernel will attempt to reclaim 971 under memory pressure. Includes SReclaimable (below), and other 972 direct allocations with a shrinker. 973 Slab: in-kernel data structures cache 974SReclaimable: Part of Slab, that might be reclaimed, such as caches 975 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 976 PageTables: amount of memory dedicated to the lowest level of page 977 tables. 978NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 979 storage 980 Bounce: Memory used for block device "bounce buffers" 981WritebackTmp: Memory used by FUSE for temporary writeback buffers 982 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 983 this is the total amount of memory currently available to 984 be allocated on the system. This limit is only adhered to 985 if strict overcommit accounting is enabled (mode 2 in 986 'vm.overcommit_memory'). 987 The CommitLimit is calculated with the following formula: 988 CommitLimit = ([total RAM pages] - [total huge TLB pages]) * 989 overcommit_ratio / 100 + [total swap pages] 990 For example, on a system with 1G of physical RAM and 7G 991 of swap with a `vm.overcommit_ratio` of 30 it would 992 yield a CommitLimit of 7.3G. 993 For more details, see the memory overcommit documentation 994 in vm/overcommit-accounting. 995Committed_AS: The amount of memory presently allocated on the system. 996 The committed memory is a sum of all of the memory which 997 has been allocated by processes, even if it has not been 998 "used" by them as of yet. A process which malloc()'s 1G 999 of memory, but only touches 300M of it will show up as 1000 using 1G. This 1G is memory which has been "committed" to 1001 by the VM and can be used at any time by the allocating 1002 application. With strict overcommit enabled on the system 1003 (mode 2 in 'vm.overcommit_memory'),allocations which would 1004 exceed the CommitLimit (detailed above) will not be permitted. 1005 This is useful if one needs to guarantee that processes will 1006 not fail due to lack of memory once that memory has been 1007 successfully allocated. 1008VmallocTotal: total size of vmalloc memory area 1009 VmallocUsed: amount of vmalloc area which is used 1010VmallocChunk: largest contiguous block of vmalloc area which is free 1011 Percpu: Memory allocated to the percpu allocator used to back percpu 1012 allocations. This stat excludes the cost of metadata. 1013 1014.............................................................................. 1015 1016vmallocinfo: 1017 1018Provides information about vmalloced/vmaped areas. One line per area, 1019containing the virtual address range of the area, size in bytes, 1020caller information of the creator, and optional information depending 1021on the kind of area : 1022 1023 pages=nr number of pages 1024 phys=addr if a physical address was specified 1025 ioremap I/O mapping (ioremap() and friends) 1026 vmalloc vmalloc() area 1027 vmap vmap()ed pages 1028 user VM_USERMAP area 1029 vpages buffer for pages pointers was vmalloced (huge area) 1030 N<node>=nr (Only on NUMA kernels) 1031 Number of pages allocated on memory node <node> 1032 1033> cat /proc/vmallocinfo 10340xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 1035 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 10360xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 1037 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 10380xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 1039 phys=7fee8000 ioremap 10400xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 1041 phys=7fee7000 ioremap 10420xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 10430xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 1044 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 10450xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 1046 pages=2 vmalloc N1=2 10470xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 1048 /0x130 [x_tables] pages=4 vmalloc N0=4 10490xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 1050 pages=14 vmalloc N2=14 10510xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 1052 pages=4 vmalloc N1=4 10530xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 1054 pages=2 vmalloc N1=2 10550xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 1056 pages=10 vmalloc N0=10 1057 1058.............................................................................. 1059 1060softirqs: 1061 1062Provides counts of softirq handlers serviced since boot time, for each cpu. 1063 1064> cat /proc/softirqs 1065 CPU0 CPU1 CPU2 CPU3 1066 HI: 0 0 0 0 1067 TIMER: 27166 27120 27097 27034 1068 NET_TX: 0 0 0 17 1069 NET_RX: 42 0 0 39 1070 BLOCK: 0 0 107 1121 1071 TASKLET: 0 0 0 290 1072 SCHED: 27035 26983 26971 26746 1073 HRTIMER: 0 0 0 0 1074 RCU: 1678 1769 2178 2250 1075 1076 10771.3 IDE devices in /proc/ide 1078---------------------------- 1079 1080The subdirectory /proc/ide contains information about all IDE devices of which 1081the kernel is aware. There is one subdirectory for each IDE controller, the 1082file drivers and a link for each IDE device, pointing to the device directory 1083in the controller specific subtree. 1084 1085The file drivers contains general information about the drivers used for the 1086IDE devices: 1087 1088 > cat /proc/ide/drivers 1089 ide-cdrom version 4.53 1090 ide-disk version 1.08 1091 1092More detailed information can be found in the controller specific 1093subdirectories. These are named ide0, ide1 and so on. Each of these 1094directories contains the files shown in table 1-6. 1095 1096 1097Table 1-6: IDE controller info in /proc/ide/ide? 1098.............................................................................. 1099 File Content 1100 channel IDE channel (0 or 1) 1101 config Configuration (only for PCI/IDE bridge) 1102 mate Mate name 1103 model Type/Chipset of IDE controller 1104.............................................................................. 1105 1106Each device connected to a controller has a separate subdirectory in the 1107controllers directory. The files listed in table 1-7 are contained in these 1108directories. 1109 1110 1111Table 1-7: IDE device information 1112.............................................................................. 1113 File Content 1114 cache The cache 1115 capacity Capacity of the medium (in 512Byte blocks) 1116 driver driver and version 1117 geometry physical and logical geometry 1118 identify device identify block 1119 media media type 1120 model device identifier 1121 settings device setup 1122 smart_thresholds IDE disk management thresholds 1123 smart_values IDE disk management values 1124.............................................................................. 1125 1126The most interesting file is settings. This file contains a nice overview of 1127the drive parameters: 1128 1129 # cat /proc/ide/ide0/hda/settings 1130 name value min max mode 1131 ---- ----- --- --- ---- 1132 bios_cyl 526 0 65535 rw 1133 bios_head 255 0 255 rw 1134 bios_sect 63 0 63 rw 1135 breada_readahead 4 0 127 rw 1136 bswap 0 0 1 r 1137 file_readahead 72 0 2097151 rw 1138 io_32bit 0 0 3 rw 1139 keepsettings 0 0 1 rw 1140 max_kb_per_request 122 1 127 rw 1141 multcount 0 0 8 rw 1142 nice1 1 0 1 rw 1143 nowerr 0 0 1 rw 1144 pio_mode write-only 0 255 w 1145 slow 0 0 1 rw 1146 unmaskirq 0 0 1 rw 1147 using_dma 0 0 1 rw 1148 1149 11501.4 Networking info in /proc/net 1151-------------------------------- 1152 1153The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 1154additional values you get for IP version 6 if you configure the kernel to 1155support this. Table 1-9 lists the files and their meaning. 1156 1157 1158Table 1-8: IPv6 info in /proc/net 1159.............................................................................. 1160 File Content 1161 udp6 UDP sockets (IPv6) 1162 tcp6 TCP sockets (IPv6) 1163 raw6 Raw device statistics (IPv6) 1164 igmp6 IP multicast addresses, which this host joined (IPv6) 1165 if_inet6 List of IPv6 interface addresses 1166 ipv6_route Kernel routing table for IPv6 1167 rt6_stats Global IPv6 routing tables statistics 1168 sockstat6 Socket statistics (IPv6) 1169 snmp6 Snmp data (IPv6) 1170.............................................................................. 1171 1172 1173Table 1-9: Network info in /proc/net 1174.............................................................................. 1175 File Content 1176 arp Kernel ARP table 1177 dev network devices with statistics 1178 dev_mcast the Layer2 multicast groups a device is listening too 1179 (interface index, label, number of references, number of bound 1180 addresses). 1181 dev_stat network device status 1182 ip_fwchains Firewall chain linkage 1183 ip_fwnames Firewall chain names 1184 ip_masq Directory containing the masquerading tables 1185 ip_masquerade Major masquerading table 1186 netstat Network statistics 1187 raw raw device statistics 1188 route Kernel routing table 1189 rpc Directory containing rpc info 1190 rt_cache Routing cache 1191 snmp SNMP data 1192 sockstat Socket statistics 1193 tcp TCP sockets 1194 udp UDP sockets 1195 unix UNIX domain sockets 1196 wireless Wireless interface data (Wavelan etc) 1197 igmp IP multicast addresses, which this host joined 1198 psched Global packet scheduler parameters. 1199 netlink List of PF_NETLINK sockets 1200 ip_mr_vifs List of multicast virtual interfaces 1201 ip_mr_cache List of multicast routing cache 1202.............................................................................. 1203 1204You can use this information to see which network devices are available in 1205your system and how much traffic was routed over those devices: 1206 1207 > cat /proc/net/dev 1208 Inter-|Receive |[... 1209 face |bytes packets errs drop fifo frame compressed multicast|[... 1210 lo: 908188 5596 0 0 0 0 0 0 [... 1211 ppp0:15475140 20721 410 0 0 410 0 0 [... 1212 eth0: 614530 7085 0 0 0 0 0 1 [... 1213 1214 ...] Transmit 1215 ...] bytes packets errs drop fifo colls carrier compressed 1216 ...] 908188 5596 0 0 0 0 0 0 1217 ...] 1375103 17405 0 0 0 0 0 0 1218 ...] 1703981 5535 0 0 0 3 0 0 1219 1220In addition, each Channel Bond interface has its own directory. For 1221example, the bond0 device will have a directory called /proc/net/bond0/. 1222It will contain information that is specific to that bond, such as the 1223current slaves of the bond, the link status of the slaves, and how 1224many times the slaves link has failed. 1225 12261.5 SCSI info 1227------------- 1228 1229If you have a SCSI host adapter in your system, you'll find a subdirectory 1230named after the driver for this adapter in /proc/scsi. You'll also see a list 1231of all recognized SCSI devices in /proc/scsi: 1232 1233 >cat /proc/scsi/scsi 1234 Attached devices: 1235 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1236 Vendor: IBM Model: DGHS09U Rev: 03E0 1237 Type: Direct-Access ANSI SCSI revision: 03 1238 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1239 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1240 Type: CD-ROM ANSI SCSI revision: 02 1241 1242 1243The directory named after the driver has one file for each adapter found in 1244the system. These files contain information about the controller, including 1245the used IRQ and the IO address range. The amount of information shown is 1246dependent on the adapter you use. The example shows the output for an Adaptec 1247AHA-2940 SCSI adapter: 1248 1249 > cat /proc/scsi/aic7xxx/0 1250 1251 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1252 Compile Options: 1253 TCQ Enabled By Default : Disabled 1254 AIC7XXX_PROC_STATS : Disabled 1255 AIC7XXX_RESET_DELAY : 5 1256 Adapter Configuration: 1257 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1258 Ultra Wide Controller 1259 PCI MMAPed I/O Base: 0xeb001000 1260 Adapter SEEPROM Config: SEEPROM found and used. 1261 Adaptec SCSI BIOS: Enabled 1262 IRQ: 10 1263 SCBs: Active 0, Max Active 2, 1264 Allocated 15, HW 16, Page 255 1265 Interrupts: 160328 1266 BIOS Control Word: 0x18b6 1267 Adapter Control Word: 0x005b 1268 Extended Translation: Enabled 1269 Disconnect Enable Flags: 0xffff 1270 Ultra Enable Flags: 0x0001 1271 Tag Queue Enable Flags: 0x0000 1272 Ordered Queue Tag Flags: 0x0000 1273 Default Tag Queue Depth: 8 1274 Tagged Queue By Device array for aic7xxx host instance 0: 1275 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1276 Actual queue depth per device for aic7xxx host instance 0: 1277 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1278 Statistics: 1279 (scsi0:0:0:0) 1280 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1281 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1282 Total transfers 160151 (74577 reads and 85574 writes) 1283 (scsi0:0:6:0) 1284 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1285 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1286 Total transfers 0 (0 reads and 0 writes) 1287 1288 12891.6 Parallel port info in /proc/parport 1290--------------------------------------- 1291 1292The directory /proc/parport contains information about the parallel ports of 1293your system. It has one subdirectory for each port, named after the port 1294number (0,1,2,...). 1295 1296These directories contain the four files shown in Table 1-10. 1297 1298 1299Table 1-10: Files in /proc/parport 1300.............................................................................. 1301 File Content 1302 autoprobe Any IEEE-1284 device ID information that has been acquired. 1303 devices list of the device drivers using that port. A + will appear by the 1304 name of the device currently using the port (it might not appear 1305 against any). 1306 hardware Parallel port's base address, IRQ line and DMA channel. 1307 irq IRQ that parport is using for that port. This is in a separate 1308 file to allow you to alter it by writing a new value in (IRQ 1309 number or none). 1310.............................................................................. 1311 13121.7 TTY info in /proc/tty 1313------------------------- 1314 1315Information about the available and actually used tty's can be found in the 1316directory /proc/tty.You'll find entries for drivers and line disciplines in 1317this directory, as shown in Table 1-11. 1318 1319 1320Table 1-11: Files in /proc/tty 1321.............................................................................. 1322 File Content 1323 drivers list of drivers and their usage 1324 ldiscs registered line disciplines 1325 driver/serial usage statistic and status of single tty lines 1326.............................................................................. 1327 1328To see which tty's are currently in use, you can simply look into the file 1329/proc/tty/drivers: 1330 1331 > cat /proc/tty/drivers 1332 pty_slave /dev/pts 136 0-255 pty:slave 1333 pty_master /dev/ptm 128 0-255 pty:master 1334 pty_slave /dev/ttyp 3 0-255 pty:slave 1335 pty_master /dev/pty 2 0-255 pty:master 1336 serial /dev/cua 5 64-67 serial:callout 1337 serial /dev/ttyS 4 64-67 serial 1338 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1339 /dev/ptmx /dev/ptmx 5 2 system 1340 /dev/console /dev/console 5 1 system:console 1341 /dev/tty /dev/tty 5 0 system:/dev/tty 1342 unknown /dev/tty 4 1-63 console 1343 1344 13451.8 Miscellaneous kernel statistics in /proc/stat 1346------------------------------------------------- 1347 1348Various pieces of information about kernel activity are available in the 1349/proc/stat file. All of the numbers reported in this file are aggregates 1350since the system first booted. For a quick look, simply cat the file: 1351 1352 > cat /proc/stat 1353 cpu 2255 34 2290 22625563 6290 127 456 0 0 0 1354 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0 1355 cpu1 1123 0 849 11313845 2614 0 18 0 0 0 1356 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1357 ctxt 1990473 1358 btime 1062191376 1359 processes 2915 1360 procs_running 1 1361 procs_blocked 0 1362 softirq 183433 0 21755 12 39 1137 231 21459 2263 1363 1364The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1365lines. These numbers identify the amount of time the CPU has spent performing 1366different kinds of work. Time units are in USER_HZ (typically hundredths of a 1367second). The meanings of the columns are as follows, from left to right: 1368 1369- user: normal processes executing in user mode 1370- nice: niced processes executing in user mode 1371- system: processes executing in kernel mode 1372- idle: twiddling thumbs 1373- iowait: In a word, iowait stands for waiting for I/O to complete. But there 1374 are several problems: 1375 1. Cpu will not wait for I/O to complete, iowait is the time that a task is 1376 waiting for I/O to complete. When cpu goes into idle state for 1377 outstanding task io, another task will be scheduled on this CPU. 1378 2. In a multi-core CPU, the task waiting for I/O to complete is not running 1379 on any CPU, so the iowait of each CPU is difficult to calculate. 1380 3. The value of iowait field in /proc/stat will decrease in certain 1381 conditions. 1382 So, the iowait is not reliable by reading from /proc/stat. 1383- irq: servicing interrupts 1384- softirq: servicing softirqs 1385- steal: involuntary wait 1386- guest: running a normal guest 1387- guest_nice: running a niced guest 1388 1389The "intr" line gives counts of interrupts serviced since boot time, for each 1390of the possible system interrupts. The first column is the total of all 1391interrupts serviced including unnumbered architecture specific interrupts; 1392each subsequent column is the total for that particular numbered interrupt. 1393Unnumbered interrupts are not shown, only summed into the total. 1394 1395The "ctxt" line gives the total number of context switches across all CPUs. 1396 1397The "btime" line gives the time at which the system booted, in seconds since 1398the Unix epoch. 1399 1400The "processes" line gives the number of processes and threads created, which 1401includes (but is not limited to) those created by calls to the fork() and 1402clone() system calls. 1403 1404The "procs_running" line gives the total number of threads that are 1405running or ready to run (i.e., the total number of runnable threads). 1406 1407The "procs_blocked" line gives the number of processes currently blocked, 1408waiting for I/O to complete. 1409 1410The "softirq" line gives counts of softirqs serviced since boot time, for each 1411of the possible system softirqs. The first column is the total of all 1412softirqs serviced; each subsequent column is the total for that particular 1413softirq. 1414 1415 14161.9 Ext4 file system parameters 1417------------------------------- 1418 1419Information about mounted ext4 file systems can be found in 1420/proc/fs/ext4. Each mounted filesystem will have a directory in 1421/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1422/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1423in Table 1-12, below. 1424 1425Table 1-12: Files in /proc/fs/ext4/<devname> 1426.............................................................................. 1427 File Content 1428 mb_groups details of multiblock allocator buddy cache of free blocks 1429.............................................................................. 1430 14312.0 /proc/consoles 1432------------------ 1433Shows registered system console lines. 1434 1435To see which character device lines are currently used for the system console 1436/dev/console, you may simply look into the file /proc/consoles: 1437 1438 > cat /proc/consoles 1439 tty0 -WU (ECp) 4:7 1440 ttyS0 -W- (Ep) 4:64 1441 1442The columns are: 1443 1444 device name of the device 1445 operations R = can do read operations 1446 W = can do write operations 1447 U = can do unblank 1448 flags E = it is enabled 1449 C = it is preferred console 1450 B = it is primary boot console 1451 p = it is used for printk buffer 1452 b = it is not a TTY but a Braille device 1453 a = it is safe to use when cpu is offline 1454 major:minor major and minor number of the device separated by a colon 1455 1456------------------------------------------------------------------------------ 1457Summary 1458------------------------------------------------------------------------------ 1459The /proc file system serves information about the running system. It not only 1460allows access to process data but also allows you to request the kernel status 1461by reading files in the hierarchy. 1462 1463The directory structure of /proc reflects the types of information and makes 1464it easy, if not obvious, where to look for specific data. 1465------------------------------------------------------------------------------ 1466 1467------------------------------------------------------------------------------ 1468CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1469------------------------------------------------------------------------------ 1470 1471------------------------------------------------------------------------------ 1472In This Chapter 1473------------------------------------------------------------------------------ 1474* Modifying kernel parameters by writing into files found in /proc/sys 1475* Exploring the files which modify certain parameters 1476* Review of the /proc/sys file tree 1477------------------------------------------------------------------------------ 1478 1479 1480A very interesting part of /proc is the directory /proc/sys. This is not only 1481a source of information, it also allows you to change parameters within the 1482kernel. Be very careful when attempting this. You can optimize your system, 1483but you can also cause it to crash. Never alter kernel parameters on a 1484production system. Set up a development machine and test to make sure that 1485everything works the way you want it to. You may have no alternative but to 1486reboot the machine once an error has been made. 1487 1488To change a value, simply echo the new value into the file. An example is 1489given below in the section on the file system data. You need to be root to do 1490this. You can create your own boot script to perform this every time your 1491system boots. 1492 1493The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1494general things in the operation of the Linux kernel. Since some of the files 1495can inadvertently disrupt your system, it is advisable to read both 1496documentation and source before actually making adjustments. In any case, be 1497very careful when writing to any of these files. The entries in /proc may 1498change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1499review the kernel documentation in the directory /usr/src/linux/Documentation. 1500This chapter is heavily based on the documentation included in the pre 2.2 1501kernels, and became part of it in version 2.2.1 of the Linux kernel. 1502 1503Please see: Documentation/admin-guide/sysctl/ directory for descriptions of these 1504entries. 1505 1506------------------------------------------------------------------------------ 1507Summary 1508------------------------------------------------------------------------------ 1509Certain aspects of kernel behavior can be modified at runtime, without the 1510need to recompile the kernel, or even to reboot the system. The files in the 1511/proc/sys tree can not only be read, but also modified. You can use the echo 1512command to write value into these files, thereby changing the default settings 1513of the kernel. 1514------------------------------------------------------------------------------ 1515 1516------------------------------------------------------------------------------ 1517CHAPTER 3: PER-PROCESS PARAMETERS 1518------------------------------------------------------------------------------ 1519 15203.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1521-------------------------------------------------------------------------------- 1522 1523These file can be used to adjust the badness heuristic used to select which 1524process gets killed in out of memory conditions. 1525 1526The badness heuristic assigns a value to each candidate task ranging from 0 1527(never kill) to 1000 (always kill) to determine which process is targeted. The 1528units are roughly a proportion along that range of allowed memory the process 1529may allocate from based on an estimation of its current memory and swap use. 1530For example, if a task is using all allowed memory, its badness score will be 15311000. If it is using half of its allowed memory, its score will be 500. 1532 1533There is an additional factor included in the badness score: the current memory 1534and swap usage is discounted by 3% for root processes. 1535 1536The amount of "allowed" memory depends on the context in which the oom killer 1537was called. If it is due to the memory assigned to the allocating task's cpuset 1538being exhausted, the allowed memory represents the set of mems assigned to that 1539cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1540memory represents the set of mempolicy nodes. If it is due to a memory 1541limit (or swap limit) being reached, the allowed memory is that configured 1542limit. Finally, if it is due to the entire system being out of memory, the 1543allowed memory represents all allocatable resources. 1544 1545The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1546is used to determine which task to kill. Acceptable values range from -1000 1547(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1548polarize the preference for oom killing either by always preferring a certain 1549task or completely disabling it. The lowest possible value, -1000, is 1550equivalent to disabling oom killing entirely for that task since it will always 1551report a badness score of 0. 1552 1553Consequently, it is very simple for userspace to define the amount of memory to 1554consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1555example, is roughly equivalent to allowing the remainder of tasks sharing the 1556same system, cpuset, mempolicy, or memory controller resources to use at least 155750% more memory. A value of -500, on the other hand, would be roughly 1558equivalent to discounting 50% of the task's allowed memory from being considered 1559as scoring against the task. 1560 1561For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1562be used to tune the badness score. Its acceptable values range from -16 1563(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1564(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1565scaled linearly with /proc/<pid>/oom_score_adj. 1566 1567The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1568value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1569requires CAP_SYS_RESOURCE. 1570 1571Caveat: when a parent task is selected, the oom killer will sacrifice any first 1572generation children with separate address spaces instead, if possible. This 1573avoids servers and important system daemons from being killed and loses the 1574minimal amount of work. 1575 1576 15773.2 /proc/<pid>/oom_score - Display current oom-killer score 1578------------------------------------------------------------- 1579 1580This file can be used to check the current score used by the oom-killer is for 1581any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which 1582process should be killed in an out-of-memory situation. 1583 1584 15853.3 /proc/<pid>/io - Display the IO accounting fields 1586------------------------------------------------------- 1587 1588This file contains IO statistics for each running process 1589 1590Example 1591------- 1592 1593test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1594[1] 3828 1595 1596test:/tmp # cat /proc/3828/io 1597rchar: 323934931 1598wchar: 323929600 1599syscr: 632687 1600syscw: 632675 1601read_bytes: 0 1602write_bytes: 323932160 1603cancelled_write_bytes: 0 1604 1605 1606Description 1607----------- 1608 1609rchar 1610----- 1611 1612I/O counter: chars read 1613The number of bytes which this task has caused to be read from storage. This 1614is simply the sum of bytes which this process passed to read() and pread(). 1615It includes things like tty IO and it is unaffected by whether or not actual 1616physical disk IO was required (the read might have been satisfied from 1617pagecache) 1618 1619 1620wchar 1621----- 1622 1623I/O counter: chars written 1624The number of bytes which this task has caused, or shall cause to be written 1625to disk. Similar caveats apply here as with rchar. 1626 1627 1628syscr 1629----- 1630 1631I/O counter: read syscalls 1632Attempt to count the number of read I/O operations, i.e. syscalls like read() 1633and pread(). 1634 1635 1636syscw 1637----- 1638 1639I/O counter: write syscalls 1640Attempt to count the number of write I/O operations, i.e. syscalls like 1641write() and pwrite(). 1642 1643 1644read_bytes 1645---------- 1646 1647I/O counter: bytes read 1648Attempt to count the number of bytes which this process really did cause to 1649be fetched from the storage layer. Done at the submit_bio() level, so it is 1650accurate for block-backed filesystems. <please add status regarding NFS and 1651CIFS at a later time> 1652 1653 1654write_bytes 1655----------- 1656 1657I/O counter: bytes written 1658Attempt to count the number of bytes which this process caused to be sent to 1659the storage layer. This is done at page-dirtying time. 1660 1661 1662cancelled_write_bytes 1663--------------------- 1664 1665The big inaccuracy here is truncate. If a process writes 1MB to a file and 1666then deletes the file, it will in fact perform no writeout. But it will have 1667been accounted as having caused 1MB of write. 1668In other words: The number of bytes which this process caused to not happen, 1669by truncating pagecache. A task can cause "negative" IO too. If this task 1670truncates some dirty pagecache, some IO which another task has been accounted 1671for (in its write_bytes) will not be happening. We _could_ just subtract that 1672from the truncating task's write_bytes, but there is information loss in doing 1673that. 1674 1675 1676Note 1677---- 1678 1679At its current implementation state, this is a bit racy on 32-bit machines: if 1680process A reads process B's /proc/pid/io while process B is updating one of 1681those 64-bit counters, process A could see an intermediate result. 1682 1683 1684More information about this can be found within the taskstats documentation in 1685Documentation/accounting. 1686 16873.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1688--------------------------------------------------------------- 1689When a process is dumped, all anonymous memory is written to a core file as 1690long as the size of the core file isn't limited. But sometimes we don't want 1691to dump some memory segments, for example, huge shared memory or DAX. 1692Conversely, sometimes we want to save file-backed memory segments into a core 1693file, not only the individual files. 1694 1695/proc/<pid>/coredump_filter allows you to customize which memory segments 1696will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1697of memory types. If a bit of the bitmask is set, memory segments of the 1698corresponding memory type are dumped, otherwise they are not dumped. 1699 1700The following 9 memory types are supported: 1701 - (bit 0) anonymous private memory 1702 - (bit 1) anonymous shared memory 1703 - (bit 2) file-backed private memory 1704 - (bit 3) file-backed shared memory 1705 - (bit 4) ELF header pages in file-backed private memory areas (it is 1706 effective only if the bit 2 is cleared) 1707 - (bit 5) hugetlb private memory 1708 - (bit 6) hugetlb shared memory 1709 - (bit 7) DAX private memory 1710 - (bit 8) DAX shared memory 1711 1712 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1713 are always dumped regardless of the bitmask status. 1714 1715 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is 1716 only affected by bit 5-6, and DAX is only affected by bits 7-8. 1717 1718The default value of coredump_filter is 0x33; this means all anonymous memory 1719segments, ELF header pages and hugetlb private memory are dumped. 1720 1721If you don't want to dump all shared memory segments attached to pid 1234, 1722write 0x31 to the process's proc file. 1723 1724 $ echo 0x31 > /proc/1234/coredump_filter 1725 1726When a new process is created, the process inherits the bitmask status from its 1727parent. It is useful to set up coredump_filter before the program runs. 1728For example: 1729 1730 $ echo 0x7 > /proc/self/coredump_filter 1731 $ ./some_program 1732 17333.5 /proc/<pid>/mountinfo - Information about mounts 1734-------------------------------------------------------- 1735 1736This file contains lines of the form: 1737 173836 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1739(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1740 1741(1) mount ID: unique identifier of the mount (may be reused after umount) 1742(2) parent ID: ID of parent (or of self for the top of the mount tree) 1743(3) major:minor: value of st_dev for files on filesystem 1744(4) root: root of the mount within the filesystem 1745(5) mount point: mount point relative to the process's root 1746(6) mount options: per mount options 1747(7) optional fields: zero or more fields of the form "tag[:value]" 1748(8) separator: marks the end of the optional fields 1749(9) filesystem type: name of filesystem of the form "type[.subtype]" 1750(10) mount source: filesystem specific information or "none" 1751(11) super options: per super block options 1752 1753Parsers should ignore all unrecognised optional fields. Currently the 1754possible optional fields are: 1755 1756shared:X mount is shared in peer group X 1757master:X mount is slave to peer group X 1758propagate_from:X mount is slave and receives propagation from peer group X (*) 1759unbindable mount is unbindable 1760 1761(*) X is the closest dominant peer group under the process's root. If 1762X is the immediate master of the mount, or if there's no dominant peer 1763group under the same root, then only the "master:X" field is present 1764and not the "propagate_from:X" field. 1765 1766For more information on mount propagation see: 1767 1768 Documentation/filesystems/sharedsubtree.txt 1769 1770 17713.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1772-------------------------------------------------------- 1773These files provide a method to access a tasks comm value. It also allows for 1774a task to set its own or one of its thread siblings comm value. The comm value 1775is limited in size compared to the cmdline value, so writing anything longer 1776then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1777comm value. 1778 1779 17803.7 /proc/<pid>/task/<tid>/children - Information about task children 1781------------------------------------------------------------------------- 1782This file provides a fast way to retrieve first level children pids 1783of a task pointed by <pid>/<tid> pair. The format is a space separated 1784stream of pids. 1785 1786Note the "first level" here -- if a child has own children they will 1787not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children 1788to obtain the descendants. 1789 1790Since this interface is intended to be fast and cheap it doesn't 1791guarantee to provide precise results and some children might be 1792skipped, especially if they've exited right after we printed their 1793pids, so one need to either stop or freeze processes being inspected 1794if precise results are needed. 1795 1796 17973.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 1798--------------------------------------------------------------- 1799This file provides information associated with an opened file. The regular 1800files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos' 1801represents the current offset of the opened file in decimal form [see lseek(2) 1802for details], 'flags' denotes the octal O_xxx mask the file has been 1803created with [see open(2) for details] and 'mnt_id' represents mount ID of 1804the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo 1805for details]. 1806 1807A typical output is 1808 1809 pos: 0 1810 flags: 0100002 1811 mnt_id: 19 1812 1813All locks associated with a file descriptor are shown in its fdinfo too. 1814 1815lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF 1816 1817The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags 1818pair provide additional information particular to the objects they represent. 1819 1820 Eventfd files 1821 ~~~~~~~~~~~~~ 1822 pos: 0 1823 flags: 04002 1824 mnt_id: 9 1825 eventfd-count: 5a 1826 1827 where 'eventfd-count' is hex value of a counter. 1828 1829 Signalfd files 1830 ~~~~~~~~~~~~~~ 1831 pos: 0 1832 flags: 04002 1833 mnt_id: 9 1834 sigmask: 0000000000000200 1835 1836 where 'sigmask' is hex value of the signal mask associated 1837 with a file. 1838 1839 Epoll files 1840 ~~~~~~~~~~~ 1841 pos: 0 1842 flags: 02 1843 mnt_id: 9 1844 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 1845 1846 where 'tfd' is a target file descriptor number in decimal form, 1847 'events' is events mask being watched and the 'data' is data 1848 associated with a target [see epoll(7) for more details]. 1849 1850 The 'pos' is current offset of the target file in decimal form 1851 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers 1852 where target file resides, all in hex format. 1853 1854 Fsnotify files 1855 ~~~~~~~~~~~~~~ 1856 For inotify files the format is the following 1857 1858 pos: 0 1859 flags: 02000000 1860 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d 1861 1862 where 'wd' is a watch descriptor in decimal form, ie a target file 1863 descriptor number, 'ino' and 'sdev' are inode and device where the 1864 target file resides and the 'mask' is the mask of events, all in hex 1865 form [see inotify(7) for more details]. 1866 1867 If the kernel was built with exportfs support, the path to the target 1868 file is encoded as a file handle. The file handle is provided by three 1869 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex 1870 format. 1871 1872 If the kernel is built without exportfs support the file handle won't be 1873 printed out. 1874 1875 If there is no inotify mark attached yet the 'inotify' line will be omitted. 1876 1877 For fanotify files the format is 1878 1879 pos: 0 1880 flags: 02 1881 mnt_id: 9 1882 fanotify flags:10 event-flags:0 1883 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 1884 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 1885 1886 where fanotify 'flags' and 'event-flags' are values used in fanotify_init 1887 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of 1888 flags associated with mark which are tracked separately from events 1889 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events 1890 mask and 'ignored_mask' is the mask of events which are to be ignored. 1891 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' 1892 does provide information about flags and mask used in fanotify_mark 1893 call [see fsnotify manpage for details]. 1894 1895 While the first three lines are mandatory and always printed, the rest is 1896 optional and may be omitted if no marks created yet. 1897 1898 Timerfd files 1899 ~~~~~~~~~~~~~ 1900 1901 pos: 0 1902 flags: 02 1903 mnt_id: 9 1904 clockid: 0 1905 ticks: 0 1906 settime flags: 01 1907 it_value: (0, 49406829) 1908 it_interval: (1, 0) 1909 1910 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations 1911 that have occurred [see timerfd_create(2) for details]. 'settime flags' are 1912 flags in octal form been used to setup the timer [see timerfd_settime(2) for 1913 details]. 'it_value' is remaining time until the timer exiration. 1914 'it_interval' is the interval for the timer. Note the timer might be set up 1915 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value' 1916 still exhibits timer's remaining time. 1917 19183.9 /proc/<pid>/map_files - Information about memory mapped files 1919--------------------------------------------------------------------- 1920This directory contains symbolic links which represent memory mapped files 1921the process is maintaining. Example output: 1922 1923 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so 1924 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so 1925 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so 1926 | ... 1927 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1 1928 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls 1929 1930The name of a link represents the virtual memory bounds of a mapping, i.e. 1931vm_area_struct::vm_start-vm_area_struct::vm_end. 1932 1933The main purpose of the map_files is to retrieve a set of memory mapped 1934files in a fast way instead of parsing /proc/<pid>/maps or 1935/proc/<pid>/smaps, both of which contain many more records. At the same 1936time one can open(2) mappings from the listings of two processes and 1937comparing their inode numbers to figure out which anonymous memory areas 1938are actually shared. 1939 19403.10 /proc/<pid>/timerslack_ns - Task timerslack value 1941--------------------------------------------------------- 1942This file provides the value of the task's timerslack value in nanoseconds. 1943This value specifies a amount of time that normal timers may be deferred 1944in order to coalesce timers and avoid unnecessary wakeups. 1945 1946This allows a task's interactivity vs power consumption trade off to be 1947adjusted. 1948 1949Writing 0 to the file will set the tasks timerslack to the default value. 1950 1951Valid values are from 0 - ULLONG_MAX 1952 1953An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level 1954permissions on the task specified to change its timerslack_ns value. 1955 19563.11 /proc/<pid>/patch_state - Livepatch patch operation state 1957----------------------------------------------------------------- 1958When CONFIG_LIVEPATCH is enabled, this file displays the value of the 1959patch state for the task. 1960 1961A value of '-1' indicates that no patch is in transition. 1962 1963A value of '0' indicates that a patch is in transition and the task is 1964unpatched. If the patch is being enabled, then the task hasn't been 1965patched yet. If the patch is being disabled, then the task has already 1966been unpatched. 1967 1968A value of '1' indicates that a patch is in transition and the task is 1969patched. If the patch is being enabled, then the task has already been 1970patched. If the patch is being disabled, then the task hasn't been 1971unpatched yet. 1972 19733.12 /proc/<pid>/arch_status - task architecture specific status 1974------------------------------------------------------------------- 1975When CONFIG_PROC_PID_ARCH_STATUS is enabled, this file displays the 1976architecture specific status of the task. 1977 1978Example 1979------- 1980 $ cat /proc/6753/arch_status 1981 AVX512_elapsed_ms: 8 1982 1983Description 1984----------- 1985 1986x86 specific entries: 1987--------------------- 1988 AVX512_elapsed_ms: 1989 ------------------ 1990 If AVX512 is supported on the machine, this entry shows the milliseconds 1991 elapsed since the last time AVX512 usage was recorded. The recording 1992 happens on a best effort basis when a task is scheduled out. This means 1993 that the value depends on two factors: 1994 1995 1) The time which the task spent on the CPU without being scheduled 1996 out. With CPU isolation and a single runnable task this can take 1997 several seconds. 1998 1999 2) The time since the task was scheduled out last. Depending on the 2000 reason for being scheduled out (time slice exhausted, syscall ...) 2001 this can be arbitrary long time. 2002 2003 As a consequence the value cannot be considered precise and authoritative 2004 information. The application which uses this information has to be aware 2005 of the overall scenario on the system in order to determine whether a 2006 task is a real AVX512 user or not. Precise information can be obtained 2007 with performance counters. 2008 2009 A special value of '-1' indicates that no AVX512 usage was recorded, thus 2010 the task is unlikely an AVX512 user, but depends on the workload and the 2011 scheduling scenario, it also could be a false negative mentioned above. 2012 2013------------------------------------------------------------------------------ 2014Configuring procfs 2015------------------------------------------------------------------------------ 2016 20174.1 Mount options 2018--------------------- 2019 2020The following mount options are supported: 2021 2022 hidepid= Set /proc/<pid>/ access mode. 2023 gid= Set the group authorized to learn processes information. 2024 2025hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories 2026(default). 2027 2028hidepid=1 means users may not access any /proc/<pid>/ directories but their 2029own. Sensitive files like cmdline, sched*, status are now protected against 2030other users. This makes it impossible to learn whether any user runs 2031specific program (given the program doesn't reveal itself by its behaviour). 2032As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, 2033poorly written programs passing sensitive information via program arguments are 2034now protected against local eavesdroppers. 2035 2036hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other 2037users. It doesn't mean that it hides a fact whether a process with a specific 2038pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), 2039but it hides process' uid and gid, which may be learned by stat()'ing 2040/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering 2041information about running processes, whether some daemon runs with elevated 2042privileges, whether other user runs some sensitive program, whether other users 2043run any program at all, etc. 2044 2045gid= defines a group authorized to learn processes information otherwise 2046prohibited by hidepid=. If you use some daemon like identd which needs to learn 2047information about processes information, just add identd to this group. 2048
