1 /*
2 * linux/kernel/profile.c
3 * Simple profiling. Manages a direct-mapped profile hit count buffer,
4 * with configurable resolution, support for restricting the cpus on
5 * which profiling is done, and switching between cpu time and
6 * schedule() calls via kernel command line parameters passed at boot.
7 *
8 * Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
9 * Red Hat, July 2004
10 * Consolidation of architecture support code for profiling,
11 * Nadia Yvette Chambers, Oracle, July 2004
12 * Amortized hit count accounting via per-cpu open-addressed hashtables
13 * to resolve timer interrupt livelocks, Nadia Yvette Chambers,
14 * Oracle, 2004
15 */
16
17 #include <linux/export.h>
18 #include <linux/profile.h>
19 #include <linux/bootmem.h>
20 #include <linux/notifier.h>
21 #include <linux/mm.h>
22 #include <linux/cpumask.h>
23 #include <linux/cpu.h>
24 #include <linux/highmem.h>
25 #include <linux/mutex.h>
26 #include <linux/slab.h>
27 #include <linux/vmalloc.h>
28 #include <linux/sched/stat.h>
29
30 #include <asm/sections.h>
31 #include <asm/irq_regs.h>
32 #include <asm/ptrace.h>
33
34 struct profile_hit {
35 u32 pc, hits;
36 };
37 #define PROFILE_GRPSHIFT 3
38 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
39 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
40 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
41
42 static atomic_t *prof_buffer;
43 static unsigned long prof_len, prof_shift;
44
45 int prof_on __read_mostly;
46 EXPORT_SYMBOL_GPL(prof_on);
47
48 static cpumask_var_t prof_cpu_mask;
49 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
50 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
51 static DEFINE_PER_CPU(int, cpu_profile_flip);
52 static DEFINE_MUTEX(profile_flip_mutex);
53 #endif /* CONFIG_SMP */
54
profile_setup(char * str)55 int profile_setup(char *str)
56 {
57 static const char schedstr[] = "schedule";
58 static const char sleepstr[] = "sleep";
59 static const char kvmstr[] = "kvm";
60 int par;
61
62 if (!strncmp(str, sleepstr, strlen(sleepstr))) {
63 #ifdef CONFIG_SCHEDSTATS
64 force_schedstat_enabled();
65 prof_on = SLEEP_PROFILING;
66 if (str[strlen(sleepstr)] == ',')
67 str += strlen(sleepstr) + 1;
68 if (get_option(&str, &par))
69 prof_shift = par;
70 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
71 prof_shift);
72 #else
73 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
74 #endif /* CONFIG_SCHEDSTATS */
75 } else if (!strncmp(str, schedstr, strlen(schedstr))) {
76 prof_on = SCHED_PROFILING;
77 if (str[strlen(schedstr)] == ',')
78 str += strlen(schedstr) + 1;
79 if (get_option(&str, &par))
80 prof_shift = par;
81 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
82 prof_shift);
83 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
84 prof_on = KVM_PROFILING;
85 if (str[strlen(kvmstr)] == ',')
86 str += strlen(kvmstr) + 1;
87 if (get_option(&str, &par))
88 prof_shift = par;
89 pr_info("kernel KVM profiling enabled (shift: %ld)\n",
90 prof_shift);
91 } else if (get_option(&str, &par)) {
92 prof_shift = par;
93 prof_on = CPU_PROFILING;
94 pr_info("kernel profiling enabled (shift: %ld)\n",
95 prof_shift);
96 }
97 return 1;
98 }
99 __setup("profile=", profile_setup);
100
101
profile_init(void)102 int __ref profile_init(void)
103 {
104 int buffer_bytes;
105 if (!prof_on)
106 return 0;
107
108 /* only text is profiled */
109 prof_len = (_etext - _stext) >> prof_shift;
110 buffer_bytes = prof_len*sizeof(atomic_t);
111
112 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
113 return -ENOMEM;
114
115 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
116
117 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
118 if (prof_buffer)
119 return 0;
120
121 prof_buffer = alloc_pages_exact(buffer_bytes,
122 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
123 if (prof_buffer)
124 return 0;
125
126 prof_buffer = vzalloc(buffer_bytes);
127 if (prof_buffer)
128 return 0;
129
130 free_cpumask_var(prof_cpu_mask);
131 return -ENOMEM;
132 }
133
134 /* Profile event notifications */
135
136 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
137 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
138 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
139
profile_task_exit(struct task_struct * task)140 void profile_task_exit(struct task_struct *task)
141 {
142 blocking_notifier_call_chain(&task_exit_notifier, 0, task);
143 }
144
profile_handoff_task(struct task_struct * task)145 int profile_handoff_task(struct task_struct *task)
146 {
147 int ret;
148 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
149 return (ret == NOTIFY_OK) ? 1 : 0;
150 }
151
profile_munmap(unsigned long addr)152 void profile_munmap(unsigned long addr)
153 {
154 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
155 }
156
task_handoff_register(struct notifier_block * n)157 int task_handoff_register(struct notifier_block *n)
158 {
159 return atomic_notifier_chain_register(&task_free_notifier, n);
160 }
161 EXPORT_SYMBOL_GPL(task_handoff_register);
162
task_handoff_unregister(struct notifier_block * n)163 int task_handoff_unregister(struct notifier_block *n)
164 {
165 return atomic_notifier_chain_unregister(&task_free_notifier, n);
166 }
167 EXPORT_SYMBOL_GPL(task_handoff_unregister);
168
profile_event_register(enum profile_type type,struct notifier_block * n)169 int profile_event_register(enum profile_type type, struct notifier_block *n)
170 {
171 int err = -EINVAL;
172
173 switch (type) {
174 case PROFILE_TASK_EXIT:
175 err = blocking_notifier_chain_register(
176 &task_exit_notifier, n);
177 break;
178 case PROFILE_MUNMAP:
179 err = blocking_notifier_chain_register(
180 &munmap_notifier, n);
181 break;
182 }
183
184 return err;
185 }
186 EXPORT_SYMBOL_GPL(profile_event_register);
187
profile_event_unregister(enum profile_type type,struct notifier_block * n)188 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
189 {
190 int err = -EINVAL;
191
192 switch (type) {
193 case PROFILE_TASK_EXIT:
194 err = blocking_notifier_chain_unregister(
195 &task_exit_notifier, n);
196 break;
197 case PROFILE_MUNMAP:
198 err = blocking_notifier_chain_unregister(
199 &munmap_notifier, n);
200 break;
201 }
202
203 return err;
204 }
205 EXPORT_SYMBOL_GPL(profile_event_unregister);
206
207 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
208 /*
209 * Each cpu has a pair of open-addressed hashtables for pending
210 * profile hits. read_profile() IPI's all cpus to request them
211 * to flip buffers and flushes their contents to prof_buffer itself.
212 * Flip requests are serialized by the profile_flip_mutex. The sole
213 * use of having a second hashtable is for avoiding cacheline
214 * contention that would otherwise happen during flushes of pending
215 * profile hits required for the accuracy of reported profile hits
216 * and so resurrect the interrupt livelock issue.
217 *
218 * The open-addressed hashtables are indexed by profile buffer slot
219 * and hold the number of pending hits to that profile buffer slot on
220 * a cpu in an entry. When the hashtable overflows, all pending hits
221 * are accounted to their corresponding profile buffer slots with
222 * atomic_add() and the hashtable emptied. As numerous pending hits
223 * may be accounted to a profile buffer slot in a hashtable entry,
224 * this amortizes a number of atomic profile buffer increments likely
225 * to be far larger than the number of entries in the hashtable,
226 * particularly given that the number of distinct profile buffer
227 * positions to which hits are accounted during short intervals (e.g.
228 * several seconds) is usually very small. Exclusion from buffer
229 * flipping is provided by interrupt disablement (note that for
230 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
231 * process context).
232 * The hash function is meant to be lightweight as opposed to strong,
233 * and was vaguely inspired by ppc64 firmware-supported inverted
234 * pagetable hash functions, but uses a full hashtable full of finite
235 * collision chains, not just pairs of them.
236 *
237 * -- nyc
238 */
__profile_flip_buffers(void * unused)239 static void __profile_flip_buffers(void *unused)
240 {
241 int cpu = smp_processor_id();
242
243 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
244 }
245
profile_flip_buffers(void)246 static void profile_flip_buffers(void)
247 {
248 int i, j, cpu;
249
250 mutex_lock(&profile_flip_mutex);
251 j = per_cpu(cpu_profile_flip, get_cpu());
252 put_cpu();
253 on_each_cpu(__profile_flip_buffers, NULL, 1);
254 for_each_online_cpu(cpu) {
255 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
256 for (i = 0; i < NR_PROFILE_HIT; ++i) {
257 if (!hits[i].hits) {
258 if (hits[i].pc)
259 hits[i].pc = 0;
260 continue;
261 }
262 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
263 hits[i].hits = hits[i].pc = 0;
264 }
265 }
266 mutex_unlock(&profile_flip_mutex);
267 }
268
profile_discard_flip_buffers(void)269 static void profile_discard_flip_buffers(void)
270 {
271 int i, cpu;
272
273 mutex_lock(&profile_flip_mutex);
274 i = per_cpu(cpu_profile_flip, get_cpu());
275 put_cpu();
276 on_each_cpu(__profile_flip_buffers, NULL, 1);
277 for_each_online_cpu(cpu) {
278 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
279 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
280 }
281 mutex_unlock(&profile_flip_mutex);
282 }
283
do_profile_hits(int type,void * __pc,unsigned int nr_hits)284 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
285 {
286 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
287 int i, j, cpu;
288 struct profile_hit *hits;
289
290 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
291 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
292 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
293 cpu = get_cpu();
294 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
295 if (!hits) {
296 put_cpu();
297 return;
298 }
299 /*
300 * We buffer the global profiler buffer into a per-CPU
301 * queue and thus reduce the number of global (and possibly
302 * NUMA-alien) accesses. The write-queue is self-coalescing:
303 */
304 local_irq_save(flags);
305 do {
306 for (j = 0; j < PROFILE_GRPSZ; ++j) {
307 if (hits[i + j].pc == pc) {
308 hits[i + j].hits += nr_hits;
309 goto out;
310 } else if (!hits[i + j].hits) {
311 hits[i + j].pc = pc;
312 hits[i + j].hits = nr_hits;
313 goto out;
314 }
315 }
316 i = (i + secondary) & (NR_PROFILE_HIT - 1);
317 } while (i != primary);
318
319 /*
320 * Add the current hit(s) and flush the write-queue out
321 * to the global buffer:
322 */
323 atomic_add(nr_hits, &prof_buffer[pc]);
324 for (i = 0; i < NR_PROFILE_HIT; ++i) {
325 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
326 hits[i].pc = hits[i].hits = 0;
327 }
328 out:
329 local_irq_restore(flags);
330 put_cpu();
331 }
332
profile_dead_cpu(unsigned int cpu)333 static int profile_dead_cpu(unsigned int cpu)
334 {
335 struct page *page;
336 int i;
337
338 if (prof_cpu_mask != NULL)
339 cpumask_clear_cpu(cpu, prof_cpu_mask);
340
341 for (i = 0; i < 2; i++) {
342 if (per_cpu(cpu_profile_hits, cpu)[i]) {
343 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
344 per_cpu(cpu_profile_hits, cpu)[i] = NULL;
345 __free_page(page);
346 }
347 }
348 return 0;
349 }
350
profile_prepare_cpu(unsigned int cpu)351 static int profile_prepare_cpu(unsigned int cpu)
352 {
353 int i, node = cpu_to_mem(cpu);
354 struct page *page;
355
356 per_cpu(cpu_profile_flip, cpu) = 0;
357
358 for (i = 0; i < 2; i++) {
359 if (per_cpu(cpu_profile_hits, cpu)[i])
360 continue;
361
362 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
363 if (!page) {
364 profile_dead_cpu(cpu);
365 return -ENOMEM;
366 }
367 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
368
369 }
370 return 0;
371 }
372
profile_online_cpu(unsigned int cpu)373 static int profile_online_cpu(unsigned int cpu)
374 {
375 if (prof_cpu_mask != NULL)
376 cpumask_set_cpu(cpu, prof_cpu_mask);
377
378 return 0;
379 }
380
381 #else /* !CONFIG_SMP */
382 #define profile_flip_buffers() do { } while (0)
383 #define profile_discard_flip_buffers() do { } while (0)
384
do_profile_hits(int type,void * __pc,unsigned int nr_hits)385 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
386 {
387 unsigned long pc;
388 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
389 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
390 }
391 #endif /* !CONFIG_SMP */
392
profile_hits(int type,void * __pc,unsigned int nr_hits)393 void profile_hits(int type, void *__pc, unsigned int nr_hits)
394 {
395 if (prof_on != type || !prof_buffer)
396 return;
397 do_profile_hits(type, __pc, nr_hits);
398 }
399 EXPORT_SYMBOL_GPL(profile_hits);
400
profile_tick(int type)401 void profile_tick(int type)
402 {
403 struct pt_regs *regs = get_irq_regs();
404
405 if (!user_mode(regs) && prof_cpu_mask != NULL &&
406 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
407 profile_hit(type, (void *)profile_pc(regs));
408 }
409
410 #ifdef CONFIG_PROC_FS
411 #include <linux/proc_fs.h>
412 #include <linux/seq_file.h>
413 #include <linux/uaccess.h>
414
prof_cpu_mask_proc_show(struct seq_file * m,void * v)415 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
416 {
417 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
418 return 0;
419 }
420
prof_cpu_mask_proc_open(struct inode * inode,struct file * file)421 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
422 {
423 return single_open(file, prof_cpu_mask_proc_show, NULL);
424 }
425
prof_cpu_mask_proc_write(struct file * file,const char __user * buffer,size_t count,loff_t * pos)426 static ssize_t prof_cpu_mask_proc_write(struct file *file,
427 const char __user *buffer, size_t count, loff_t *pos)
428 {
429 cpumask_var_t new_value;
430 int err;
431
432 if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
433 return -ENOMEM;
434
435 err = cpumask_parse_user(buffer, count, new_value);
436 if (!err) {
437 cpumask_copy(prof_cpu_mask, new_value);
438 err = count;
439 }
440 free_cpumask_var(new_value);
441 return err;
442 }
443
444 static const struct file_operations prof_cpu_mask_proc_fops = {
445 .open = prof_cpu_mask_proc_open,
446 .read = seq_read,
447 .llseek = seq_lseek,
448 .release = single_release,
449 .write = prof_cpu_mask_proc_write,
450 };
451
create_prof_cpu_mask(void)452 void create_prof_cpu_mask(void)
453 {
454 /* create /proc/irq/prof_cpu_mask */
455 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
456 }
457
458 /*
459 * This function accesses profiling information. The returned data is
460 * binary: the sampling step and the actual contents of the profile
461 * buffer. Use of the program readprofile is recommended in order to
462 * get meaningful info out of these data.
463 */
464 static ssize_t
read_profile(struct file * file,char __user * buf,size_t count,loff_t * ppos)465 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
466 {
467 unsigned long p = *ppos;
468 ssize_t read;
469 char *pnt;
470 unsigned int sample_step = 1 << prof_shift;
471
472 profile_flip_buffers();
473 if (p >= (prof_len+1)*sizeof(unsigned int))
474 return 0;
475 if (count > (prof_len+1)*sizeof(unsigned int) - p)
476 count = (prof_len+1)*sizeof(unsigned int) - p;
477 read = 0;
478
479 while (p < sizeof(unsigned int) && count > 0) {
480 if (put_user(*((char *)(&sample_step)+p), buf))
481 return -EFAULT;
482 buf++; p++; count--; read++;
483 }
484 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
485 if (copy_to_user(buf, (void *)pnt, count))
486 return -EFAULT;
487 read += count;
488 *ppos += read;
489 return read;
490 }
491
492 /*
493 * Writing to /proc/profile resets the counters
494 *
495 * Writing a 'profiling multiplier' value into it also re-sets the profiling
496 * interrupt frequency, on architectures that support this.
497 */
write_profile(struct file * file,const char __user * buf,size_t count,loff_t * ppos)498 static ssize_t write_profile(struct file *file, const char __user *buf,
499 size_t count, loff_t *ppos)
500 {
501 #ifdef CONFIG_SMP
502 extern int setup_profiling_timer(unsigned int multiplier);
503
504 if (count == sizeof(int)) {
505 unsigned int multiplier;
506
507 if (copy_from_user(&multiplier, buf, sizeof(int)))
508 return -EFAULT;
509
510 if (setup_profiling_timer(multiplier))
511 return -EINVAL;
512 }
513 #endif
514 profile_discard_flip_buffers();
515 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
516 return count;
517 }
518
519 static const struct file_operations proc_profile_operations = {
520 .read = read_profile,
521 .write = write_profile,
522 .llseek = default_llseek,
523 };
524
create_proc_profile(void)525 int __ref create_proc_profile(void)
526 {
527 struct proc_dir_entry *entry;
528 #ifdef CONFIG_SMP
529 enum cpuhp_state online_state;
530 #endif
531
532 int err = 0;
533
534 if (!prof_on)
535 return 0;
536 #ifdef CONFIG_SMP
537 err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
538 profile_prepare_cpu, profile_dead_cpu);
539 if (err)
540 return err;
541
542 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
543 profile_online_cpu, NULL);
544 if (err < 0)
545 goto err_state_prep;
546 online_state = err;
547 err = 0;
548 #endif
549 entry = proc_create("profile", S_IWUSR | S_IRUGO,
550 NULL, &proc_profile_operations);
551 if (!entry)
552 goto err_state_onl;
553 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
554
555 return err;
556 err_state_onl:
557 #ifdef CONFIG_SMP
558 cpuhp_remove_state(online_state);
559 err_state_prep:
560 cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
561 #endif
562 return err;
563 }
564 subsys_initcall(create_proc_profile);
565 #endif /* CONFIG_PROC_FS */
566
