Lines Matching +full:non +full:- +full:descriptive
1 .. _cgroup-v2:
11 conventions of cgroup v2. It describes all userland-visible aspects
14 v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgroup-v1>`.
19 1-1. Terminology
20 1-2. What is cgroup?
22 2-1. Mounting
23 2-2. Organizing Processes and Threads
24 2-2-1. Processes
25 2-2-2. Threads
26 2-3. [Un]populated Notification
27 2-4. Controlling Controllers
28 2-4-1. Enabling and Disabling
29 2-4-2. Top-down Constraint
30 2-4-3. No Internal Process Constraint
31 2-5. Delegation
32 2-5-1. Model of Delegation
33 2-5-2. Delegation Containment
34 2-6. Guidelines
35 2-6-1. Organize Once and Control
36 2-6-2. Avoid Name Collisions
38 3-1. Weights
39 3-2. Limits
40 3-3. Protections
41 3-4. Allocations
43 4-1. Format
44 4-2. Conventions
45 4-3. Core Interface Files
47 5-1. CPU
48 5-1-1. CPU Interface Files
49 5-2. Memory
50 5-2-1. Memory Interface Files
51 5-2-2. Usage Guidelines
52 5-2-3. Memory Ownership
53 5-3. IO
54 5-3-1. IO Interface Files
55 5-3-2. Writeback
56 5-3-3. IO Latency
57 5-3-3-1. How IO Latency Throttling Works
58 5-3-3-2. IO Latency Interface Files
59 5-3-4. IO Priority
60 5-4. PID
61 5-4-1. PID Interface Files
62 5-5. Cpuset
63 5.5-1. Cpuset Interface Files
64 5-6. Device
65 5-7. RDMA
66 5-7-1. RDMA Interface Files
67 5-8. HugeTLB
68 5.8-1. HugeTLB Interface Files
69 5-9. Misc
70 5.9-1 Miscellaneous cgroup Interface Files
71 5.9-2 Migration and Ownership
72 5-10. Others
73 5-10-1. perf_event
74 5-N. Non-normative information
75 5-N-1. CPU controller root cgroup process behaviour
76 5-N-2. IO controller root cgroup process behaviour
78 6-1. Basics
79 6-2. The Root and Views
80 6-3. Migration and setns(2)
81 6-4. Interaction with Other Namespaces
83 P-1. Filesystem Support for Writeback
86 R-1. Multiple Hierarchies
87 R-2. Thread Granularity
88 R-3. Competition Between Inner Nodes and Threads
89 R-4. Other Interface Issues
90 R-5. Controller Issues and Remedies
91 R-5-1. Memory
98 -----------
107 ---------------
113 cgroup is largely composed of two parts - the core and controllers.
129 hierarchical - if a controller is enabled on a cgroup, it affects all
131 sub-hierarchy of the cgroup. When a controller is enabled on a nested
141 --------
146 # mount -t cgroup2 none $MOUNT_POINT
156 is no longer referenced in its current hierarchy. Because per-cgroup
163 to inter-controller dependencies, other controllers may need to be
184 ignored on non-init namespace mounts. Please refer to the
201 option is ignored on non-init namespace mounts.
209 behavior but is a mount-option to avoid regressing setups
215 --------------------------------
221 A child cgroup can be created by creating a sub-directory::
226 structure. Each cgroup has a read-writable interface file
228 belong to the cgroup one-per-line. The PIDs are not ordered and the
259 0::/test-cgroup/test-cgroup-nested
266 0::/test-cgroup/test-cgroup-nested (deleted)
292 constraint - threaded controllers can be enabled on non-leaf cgroups
316 - As the cgroup will join the parent's resource domain. The parent
319 - When the parent is an unthreaded domain, it must not have any domain
323 Topology-wise, a cgroup can be in an invalid state. Please consider
326 A (threaded domain) - B (threaded) - C (domain, just created)
341 threads in the cgroup. Except that the operations are per-thread
342 instead of per-process, "cgroup.threads" has the same format and
364 between threads in a non-leaf cgroup and its child cgroups. Each
369 --------------------------
371 Each non-root cgroup has a "cgroup.events" file which contains
372 "populated" field indicating whether the cgroup's sub-hierarchy has
376 example, to start a clean-up operation after all processes of a given
377 sub-hierarchy have exited. The populated state updates and
378 notifications are recursive. Consider the following sub-hierarchy
382 A(4) - B(0) - C(1)
392 -----------------------
406 # echo "+cpu +memory -io" > cgroup.subtree_control
415 Consider the following sub-hierarchy. The enabled controllers are
418 A(cpu,memory) - B(memory) - C()
432 controller interface files - anything which doesn't start with
436 Top-down Constraint
439 Resources are distributed top-down and a cgroup can further distribute
441 parent. This means that all non-root "cgroup.subtree_control" files
451 Non-root cgroups can distribute domain resources to their children
466 refer to the Non-normative information section in the Controllers
479 ----------
499 delegated, the user can build sub-hierarchy under the directory,
503 happens in the delegated sub-hierarchy, nothing can escape the
507 cgroups in or nesting depth of a delegated sub-hierarchy; however,
514 A delegated sub-hierarchy is contained in the sense that processes
515 can't be moved into or out of the sub-hierarchy by the delegatee.
518 requiring the following conditions for a process with a non-root euid
522 - The writer must have write access to the "cgroup.procs" file.
524 - The writer must have write access to the "cgroup.procs" file of the
528 processes around freely in the delegated sub-hierarchy it can't pull
529 in from or push out to outside the sub-hierarchy.
535 ~~~~~~~~~~~~~ - C0 - C00
538 ~~~~~~~~~~~~~ - C1 - C10
545 will be denied with -EACCES.
550 is not reachable, the migration is rejected with -ENOENT.
554 ----------
562 inherent trade-offs between migration and various hot paths in terms
568 resource structure once on start-up. Dynamic adjustments to resource
601 -------
607 work-conserving. Due to the dynamic nature, this model is usually
623 ------
626 Limits can be over-committed - the sum of the limits of children can
631 As limits can be over-committed, all configuration combinations are
640 -----------
645 soft boundaries. Protections can also be over-committed in which case
652 As protections can be over-committed, all configuration combinations
656 "memory.low" implements best-effort memory protection and is an
661 -----------
664 resource. Allocations can't be over-committed - the sum of the
671 As allocations can't be over-committed, some configuration
676 "cpu.rt.max" hard-allocates realtime slices and is an example of this
684 ------
689 New-line separated values
697 (when read-only or multiple values can be written at once)
723 -----------
725 - Settings for a single feature should be contained in a single file.
727 - The root cgroup should be exempt from resource control and thus
730 - The default time unit is microseconds. If a different unit is ever
733 - A parts-per quantity should use a percentage decimal with at least
734 two digit fractional part - e.g. 13.40.
736 - If a controller implements weight based resource distribution, its
742 - If a controller implements an absolute resource guarantee and/or
751 - If a setting has a configurable default value and keyed specific
765 # cat cgroup-example-interface-file
771 # echo 125 > cgroup-example-interface-file
775 # echo "default 125" > cgroup-example-interface-file
779 # echo "8:16 170" > cgroup-example-interface-file
783 # echo "8:0 default" > cgroup-example-interface-file
784 # cat cgroup-example-interface-file
788 - For events which are not very high frequency, an interface file
795 --------------------
800 A read-write single value file which exists on non-root
806 - "domain" : A normal valid domain cgroup.
808 - "domain threaded" : A threaded domain cgroup which is
811 - "domain invalid" : A cgroup which is in an invalid state.
815 - "threaded" : A threaded cgroup which is a member of a
822 A read-write new-line separated values file which exists on
826 the cgroup one-per-line. The PIDs are not ordered and the
835 - It must have write access to the "cgroup.procs" file.
837 - It must have write access to the "cgroup.procs" file of the
840 When delegating a sub-hierarchy, write access to this file
848 A read-write new-line separated values file which exists on
852 the cgroup one-per-line. The TIDs are not ordered and the
861 - It must have write access to the "cgroup.threads" file.
863 - The cgroup that the thread is currently in must be in the
866 - It must have write access to the "cgroup.procs" file of the
869 When delegating a sub-hierarchy, write access to this file
873 A read-only space separated values file which exists on all
880 A read-write space separated values file which exists on all
887 Space separated list of controllers prefixed with '+' or '-'
889 name prefixed with '+' enables the controller and '-'
895 A read-only flat-keyed file which exists on non-root cgroups.
907 A read-write single value files. The default is "max".
914 A read-write single value files. The default is "max".
921 A read-only flat-keyed file with the following entries:
939 A read-write single value file which exists on non-root cgroups.
962 create new sub-cgroups.
965 A write-only single value file which exists in non-root cgroups.
977 the whole thread-group.
980 A read-write single value file that allowed values are "0" and "1".
984 Writing "1" to the file will re-enable the cgroup PSI accounting.
992 This may cause non-negligible overhead for some workloads when under
994 be used to disable PSI accounting in the non-leaf cgroups.
997 A read-write nested-keyed file.
1005 .. _cgroup-v2-cpu:
1008 ---
1036 A read-only flat-keyed file.
1041 - usage_usec
1042 - user_usec
1043 - system_usec
1047 - nr_periods
1048 - nr_throttled
1049 - throttled_usec
1050 - nr_bursts
1051 - burst_usec
1054 A read-write single value file which exists on non-root
1060 A read-write single value file which exists on non-root
1063 The nice value is in the range [-20, 19].
1072 A read-write two value file which exists on non-root cgroups.
1084 A read-write single value file which exists on non-root
1090 A read-write nested-keyed file.
1096 A read-write single value file which exists on non-root cgroups.
1111 A read-write single value file which exists on non-root cgroups.
1124 ------
1132 While not completely water-tight, all major memory usages by a given
1137 - Userland memory - page cache and anonymous memory.
1139 - Kernel data structures such as dentries and inodes.
1141 - TCP socket buffers.
1154 A read-only single value file which exists on non-root
1161 A read-write single value file which exists on non-root
1187 A read-write single value file which exists on non-root
1190 Best-effort memory protection. If the memory usage of a
1210 A read-write single value file which exists on non-root
1222 A read-write single value file which exists on non-root
1231 In default configuration regular 0-order allocations always
1236 as -ENOMEM or silently ignore in cases like disk readahead.
1243 A write-only nested-keyed file which exists for all cgroups.
1261 specified amount, -EAGAIN is returned.
1271 A read-only single value file which exists on non-root
1278 A read-write single value file which exists on non-root
1288 Tasks with the OOM protection (oom_score_adj set to -1000)
1296 A read-only flat-keyed file which exists on non-root cgroups.
1310 boundary is over-committed.
1330 considered as an option, e.g. for failed high-order
1346 A read-only flat-keyed file which exists on non-root cgroups.
1349 types of memory, type-specific details, and other information
1358 If the entry has no per-node counter (or not show in the
1359 memory.numa_stat). We use 'npn' (non-per-node) as the tag
1387 Amount of memory used for storing per-cpu kernel
1397 Amount of cached filesystem data that is swap-backed,
1434 Amount of memory, swap-backed and filesystem-backed,
1440 the value for the foo counter, since the foo counter is type-based, not
1441 list-based.
1452 Amount of memory used for storing in-kernel data
1529 A read-only nested-keyed file which exists on non-root cgroups.
1532 types of memory, type-specific details, and other information
1554 A read-only single value file which exists on non-root
1561 A read-write single value file which exists on non-root
1566 allow userspace to implement custom out-of-memory procedures.
1577 A read-write single value file which exists on non-root
1584 A read-only flat-keyed file which exists on non-root cgroups.
1600 because of running out of swap system-wide or max
1609 A read-only single value file which exists on non-root
1616 A read-write single value file which exists on non-root
1624 A read-only nested-keyed file.
1634 Over-committing on high limit (sum of high limits > available memory)
1648 pressure - how much the workload is being impacted due to lack of
1649 memory - is necessary to determine whether a workload needs more
1663 To which cgroup the area will be charged is in-deterministic; however,
1674 --
1679 only if cfq-iosched is in use and neither scheme is available for
1680 blk-mq devices.
1687 A read-only nested-keyed file.
1707 A read-write nested-keyed file which exists only on the root
1719 enable Weight-based control enable
1751 devices which show wide temporary behavior changes - e.g. a
1762 A read-write nested-keyed file which exists only on the root
1775 model The cost model in use - "linear"
1801 generate device-specific coefficients.
1804 A read-write flat-keyed file which exists on non-root cgroups.
1824 A read-write nested-keyed file which exists on non-root
1838 When writing, any number of nested key-value pairs can be
1863 A read-only nested-keyed file.
1882 writes out dirty pages for the memory domain. Both system-wide and
1883 per-cgroup dirty memory states are examined and the more restrictive
1921 memory controller and system-wide clean memory.
1954 your real setting, setting at 10-15% higher than the value in io.stat.
1964 - Queue depth throttling. This is the number of outstanding IO's a group is
1968 - Artificial delay induction. There are certain types of IO that cannot be
2015 no-change
2018 none-to-rt
2023 restrict-to-be
2034 +-------------+---+
2035 | no-change | 0 |
2036 +-------------+---+
2037 | none-to-rt | 1 |
2038 +-------------+---+
2039 | rt-to-be | 2 |
2040 +-------------+---+
2041 | all-to-idle | 3 |
2042 +-------------+---+
2046 +-------------------------------+---+
2048 +-------------------------------+---+
2049 | IOPRIO_CLASS_RT (real-time) | 1 |
2050 +-------------------------------+---+
2052 +-------------------------------+---+
2054 +-------------------------------+---+
2058 - Translate the I/O priority class policy into a number.
2059 - Change the request I/O priority class into the maximum of the I/O priority
2063 ---
2082 A read-write single value file which exists on non-root
2088 A read-only single value file which exists on all cgroups.
2098 through fork() or clone(). These will return -EAGAIN if the creation
2103 ------
2110 memory placement to reduce cross-node memory access and contention
2121 A read-write multiple values file which exists on non-root
2122 cpuset-enabled cgroups.
2129 The CPU numbers are comma-separated numbers or ranges.
2133 0-4,6,8-10
2136 setting as the nearest cgroup ancestor with a non-empty
2143 A read-only multiple values file which exists on all
2144 cpuset-enabled cgroups.
2160 A read-write multiple values file which exists on non-root
2161 cpuset-enabled cgroups.
2168 The memory node numbers are comma-separated numbers or ranges.
2172 0-1,3
2175 setting as the nearest cgroup ancestor with a non-empty
2182 Setting a non-empty value to "cpuset.mems" causes memory of
2194 A read-only multiple values file which exists on all
2195 cpuset-enabled cgroups.
2210 A read-write single value file which exists on non-root
2211 cpuset-enabled cgroups. This flag is owned by the parent cgroup
2217 "member" Non-root member of a partition
2223 cannot be changed. All other non-root cgroups start out as
2243 two possible states - valid or invalid. An invalid partition
2254 "member" Non-root member of a partition
2261 In the case of an invalid partition root, a descriptive string on
2286 A valid non-root parent partition may distribute out all its CPUs
2306 -----------------
2317 on the return value the attempt will succeed or fail with -EPERM.
2322 If the program returns 0, the attempt fails with -EPERM, otherwise it
2330 ----
2339 A readwrite nested-keyed file that exists for all the cgroups
2360 A read-only file that describes current resource usage.
2369 -------
2386 A read-only flat-keyed file which exists on non-root cgroups.
2399 use hugetlb pages are included. The per-node values are in bytes.
2402 ----
2424 A read-only flat-keyed file shown only in the root cgroup. It shows
2433 A read-only flat-keyed file shown in the non-root cgroups. It shows
2441 A read-write flat-keyed file shown in the non root cgroups. Allowed
2460 A read-only flat-keyed file which exists on non-root cgroups. The
2478 ------
2489 Non-normative information
2490 -------------------------
2506 appropriately so the neutral - nice 0 - value is 100 instead of 1024).
2522 ------
2541 The path '/batchjobs/container_id1' can be considered as system-data
2546 # ls -l /proc/self/ns/cgroup
2547 lrwxrwxrwx 1 root root 0 2014-07-15 10:37 /proc/self/ns/cgroup -> cgroup:[4026531835]
2553 # ls -l /proc/self/ns/cgroup
2554 lrwxrwxrwx 1 root root 0 2014-07-15 10:35 /proc/self/ns/cgroup -> cgroup:[4026532183]
2558 When some thread from a multi-threaded process unshares its cgroup
2570 ------------------
2581 # ~/unshare -c # unshare cgroupns in some cgroup
2589 Each process gets its namespace-specific view of "/proc/$PID/cgroup"
2620 ----------------------
2649 ---------------------------------
2652 running inside a non-init cgroup namespace::
2654 # mount -t cgroup2 none $MOUNT_POINT
2661 the view of cgroup hierarchy by namespace-private cgroupfs mount
2674 --------------------------------
2677 address_space_operations->writepage[s]() to annotate bio's using the
2694 super_block by setting SB_I_CGROUPWB in ->s_iflags. This allows for
2711 - Multiple hierarchies including named ones are not supported.
2713 - All v1 mount options are not supported.
2715 - The "tasks" file is removed and "cgroup.procs" is not sorted.
2717 - "cgroup.clone_children" is removed.
2719 - /proc/cgroups is meaningless for v2. Use "cgroup.controllers" file
2727 --------------------
2780 ------------------
2788 Generally, in-process knowledge is available only to the process
2789 itself; thus, unlike service-level organization of processes,
2796 sub-hierarchies and control resource distributions along them. This
2797 effectively raised cgroup to the status of a syscall-like API exposed
2807 that the process would actually be operating on its own sub-hierarchy.
2811 system-management pseudo filesystem. cgroup ended up with interface
2814 individual applications through the ill-defined delegation mechanism
2824 -------------------------------------------
2835 cycles and the number of internal threads fluctuated - the ratios
2851 clearly defined. There were attempts to add ad-hoc behaviors and
2865 ----------------------
2869 was how an empty cgroup was notified - a userland helper binary was
2872 to in-kernel event delivery filtering mechanism further complicating
2894 ------------------------------
2901 global reclaim prefers is opt-in, rather than opt-out. The costs for
2911 becomes self-defeating.
2913 The memory.low boundary on the other hand is a top-down allocated
2951 new limit is met - or the task writing to memory.max is killed.
2960 groups can sabotage swapping by other means - such as referencing its
2961 anonymous memory in a tight loop - and an admin can not assume full