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 <asm/sections.h>
29 #include <asm/irq_regs.h>
30 #include <asm/ptrace.h>
31
32 struct profile_hit {
33 u32 pc, hits;
34 };
35 #define PROFILE_GRPSHIFT 3
36 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
37 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
38 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
39
40 static atomic_t *prof_buffer;
41 static unsigned long prof_len;
42 static unsigned short int prof_shift;
43
44 int prof_on __read_mostly;
45 EXPORT_SYMBOL_GPL(prof_on);
46
47 static cpumask_var_t prof_cpu_mask;
48 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
49 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
50 static DEFINE_PER_CPU(int, cpu_profile_flip);
51 static DEFINE_MUTEX(profile_flip_mutex);
52 #endif /* CONFIG_SMP */
53
profile_setup(char * str)54 int profile_setup(char *str)
55 {
56 static const char schedstr[] = "schedule";
57 static const char sleepstr[] = "sleep";
58 static const char kvmstr[] = "kvm";
59 int par;
60
61 if (!strncmp(str, sleepstr, strlen(sleepstr))) {
62 #ifdef CONFIG_SCHEDSTATS
63 prof_on = SLEEP_PROFILING;
64 if (str[strlen(sleepstr)] == ',')
65 str += strlen(sleepstr) + 1;
66 if (get_option(&str, &par))
67 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
68 pr_info("kernel sleep profiling enabled (shift: %u)\n",
69 prof_shift);
70 #else
71 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
72 #endif /* CONFIG_SCHEDSTATS */
73 } else if (!strncmp(str, schedstr, strlen(schedstr))) {
74 prof_on = SCHED_PROFILING;
75 if (str[strlen(schedstr)] == ',')
76 str += strlen(schedstr) + 1;
77 if (get_option(&str, &par))
78 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
79 pr_info("kernel schedule profiling enabled (shift: %u)\n",
80 prof_shift);
81 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
82 prof_on = KVM_PROFILING;
83 if (str[strlen(kvmstr)] == ',')
84 str += strlen(kvmstr) + 1;
85 if (get_option(&str, &par))
86 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
87 pr_info("kernel KVM profiling enabled (shift: %u)\n",
88 prof_shift);
89 } else if (get_option(&str, &par)) {
90 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
91 prof_on = CPU_PROFILING;
92 pr_info("kernel profiling enabled (shift: %u)\n",
93 prof_shift);
94 }
95 return 1;
96 }
97 __setup("profile=", profile_setup);
98
99
profile_init(void)100 int __ref profile_init(void)
101 {
102 int buffer_bytes;
103 if (!prof_on)
104 return 0;
105
106 /* only text is profiled */
107 prof_len = (_etext - _stext) >> prof_shift;
108 buffer_bytes = prof_len*sizeof(atomic_t);
109
110 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
111 return -ENOMEM;
112
113 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
114
115 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
116 if (prof_buffer)
117 return 0;
118
119 prof_buffer = alloc_pages_exact(buffer_bytes,
120 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
121 if (prof_buffer)
122 return 0;
123
124 prof_buffer = vzalloc(buffer_bytes);
125 if (prof_buffer)
126 return 0;
127
128 free_cpumask_var(prof_cpu_mask);
129 return -ENOMEM;
130 }
131
132 /* Profile event notifications */
133
134 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
135 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
136 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
137
profile_task_exit(struct task_struct * task)138 void profile_task_exit(struct task_struct *task)
139 {
140 blocking_notifier_call_chain(&task_exit_notifier, 0, task);
141 }
142
profile_handoff_task(struct task_struct * task)143 int profile_handoff_task(struct task_struct *task)
144 {
145 int ret;
146 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
147 return (ret == NOTIFY_OK) ? 1 : 0;
148 }
149
profile_munmap(unsigned long addr)150 void profile_munmap(unsigned long addr)
151 {
152 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
153 }
154
task_handoff_register(struct notifier_block * n)155 int task_handoff_register(struct notifier_block *n)
156 {
157 return atomic_notifier_chain_register(&task_free_notifier, n);
158 }
159 EXPORT_SYMBOL_GPL(task_handoff_register);
160
task_handoff_unregister(struct notifier_block * n)161 int task_handoff_unregister(struct notifier_block *n)
162 {
163 return atomic_notifier_chain_unregister(&task_free_notifier, n);
164 }
165 EXPORT_SYMBOL_GPL(task_handoff_unregister);
166
profile_event_register(enum profile_type type,struct notifier_block * n)167 int profile_event_register(enum profile_type type, struct notifier_block *n)
168 {
169 int err = -EINVAL;
170
171 switch (type) {
172 case PROFILE_TASK_EXIT:
173 err = blocking_notifier_chain_register(
174 &task_exit_notifier, n);
175 break;
176 case PROFILE_MUNMAP:
177 err = blocking_notifier_chain_register(
178 &munmap_notifier, n);
179 break;
180 }
181
182 return err;
183 }
184 EXPORT_SYMBOL_GPL(profile_event_register);
185
profile_event_unregister(enum profile_type type,struct notifier_block * n)186 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
187 {
188 int err = -EINVAL;
189
190 switch (type) {
191 case PROFILE_TASK_EXIT:
192 err = blocking_notifier_chain_unregister(
193 &task_exit_notifier, n);
194 break;
195 case PROFILE_MUNMAP:
196 err = blocking_notifier_chain_unregister(
197 &munmap_notifier, n);
198 break;
199 }
200
201 return err;
202 }
203 EXPORT_SYMBOL_GPL(profile_event_unregister);
204
205 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
206 /*
207 * Each cpu has a pair of open-addressed hashtables for pending
208 * profile hits. read_profile() IPI's all cpus to request them
209 * to flip buffers and flushes their contents to prof_buffer itself.
210 * Flip requests are serialized by the profile_flip_mutex. The sole
211 * use of having a second hashtable is for avoiding cacheline
212 * contention that would otherwise happen during flushes of pending
213 * profile hits required for the accuracy of reported profile hits
214 * and so resurrect the interrupt livelock issue.
215 *
216 * The open-addressed hashtables are indexed by profile buffer slot
217 * and hold the number of pending hits to that profile buffer slot on
218 * a cpu in an entry. When the hashtable overflows, all pending hits
219 * are accounted to their corresponding profile buffer slots with
220 * atomic_add() and the hashtable emptied. As numerous pending hits
221 * may be accounted to a profile buffer slot in a hashtable entry,
222 * this amortizes a number of atomic profile buffer increments likely
223 * to be far larger than the number of entries in the hashtable,
224 * particularly given that the number of distinct profile buffer
225 * positions to which hits are accounted during short intervals (e.g.
226 * several seconds) is usually very small. Exclusion from buffer
227 * flipping is provided by interrupt disablement (note that for
228 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
229 * process context).
230 * The hash function is meant to be lightweight as opposed to strong,
231 * and was vaguely inspired by ppc64 firmware-supported inverted
232 * pagetable hash functions, but uses a full hashtable full of finite
233 * collision chains, not just pairs of them.
234 *
235 * -- nyc
236 */
__profile_flip_buffers(void * unused)237 static void __profile_flip_buffers(void *unused)
238 {
239 int cpu = smp_processor_id();
240
241 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
242 }
243
profile_flip_buffers(void)244 static void profile_flip_buffers(void)
245 {
246 int i, j, cpu;
247
248 mutex_lock(&profile_flip_mutex);
249 j = per_cpu(cpu_profile_flip, get_cpu());
250 put_cpu();
251 on_each_cpu(__profile_flip_buffers, NULL, 1);
252 for_each_online_cpu(cpu) {
253 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
254 for (i = 0; i < NR_PROFILE_HIT; ++i) {
255 if (!hits[i].hits) {
256 if (hits[i].pc)
257 hits[i].pc = 0;
258 continue;
259 }
260 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
261 hits[i].hits = hits[i].pc = 0;
262 }
263 }
264 mutex_unlock(&profile_flip_mutex);
265 }
266
profile_discard_flip_buffers(void)267 static void profile_discard_flip_buffers(void)
268 {
269 int i, cpu;
270
271 mutex_lock(&profile_flip_mutex);
272 i = per_cpu(cpu_profile_flip, get_cpu());
273 put_cpu();
274 on_each_cpu(__profile_flip_buffers, NULL, 1);
275 for_each_online_cpu(cpu) {
276 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
277 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
278 }
279 mutex_unlock(&profile_flip_mutex);
280 }
281
do_profile_hits(int type,void * __pc,unsigned int nr_hits)282 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
283 {
284 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
285 int i, j, cpu;
286 struct profile_hit *hits;
287
288 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
289 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
290 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
291 cpu = get_cpu();
292 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
293 if (!hits) {
294 put_cpu();
295 return;
296 }
297 /*
298 * We buffer the global profiler buffer into a per-CPU
299 * queue and thus reduce the number of global (and possibly
300 * NUMA-alien) accesses. The write-queue is self-coalescing:
301 */
302 local_irq_save(flags);
303 do {
304 for (j = 0; j < PROFILE_GRPSZ; ++j) {
305 if (hits[i + j].pc == pc) {
306 hits[i + j].hits += nr_hits;
307 goto out;
308 } else if (!hits[i + j].hits) {
309 hits[i + j].pc = pc;
310 hits[i + j].hits = nr_hits;
311 goto out;
312 }
313 }
314 i = (i + secondary) & (NR_PROFILE_HIT - 1);
315 } while (i != primary);
316
317 /*
318 * Add the current hit(s) and flush the write-queue out
319 * to the global buffer:
320 */
321 atomic_add(nr_hits, &prof_buffer[pc]);
322 for (i = 0; i < NR_PROFILE_HIT; ++i) {
323 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
324 hits[i].pc = hits[i].hits = 0;
325 }
326 out:
327 local_irq_restore(flags);
328 put_cpu();
329 }
330
profile_cpu_callback(struct notifier_block * info,unsigned long action,void * __cpu)331 static int profile_cpu_callback(struct notifier_block *info,
332 unsigned long action, void *__cpu)
333 {
334 int node, cpu = (unsigned long)__cpu;
335 struct page *page;
336
337 switch (action) {
338 case CPU_UP_PREPARE:
339 case CPU_UP_PREPARE_FROZEN:
340 node = cpu_to_mem(cpu);
341 per_cpu(cpu_profile_flip, cpu) = 0;
342 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
343 page = __alloc_pages_node(node,
344 GFP_KERNEL | __GFP_ZERO,
345 0);
346 if (!page)
347 return notifier_from_errno(-ENOMEM);
348 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
349 }
350 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
351 page = __alloc_pages_node(node,
352 GFP_KERNEL | __GFP_ZERO,
353 0);
354 if (!page)
355 goto out_free;
356 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
357 }
358 break;
359 out_free:
360 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
361 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
362 __free_page(page);
363 return notifier_from_errno(-ENOMEM);
364 case CPU_ONLINE:
365 case CPU_ONLINE_FROZEN:
366 if (prof_cpu_mask != NULL)
367 cpumask_set_cpu(cpu, prof_cpu_mask);
368 break;
369 case CPU_UP_CANCELED:
370 case CPU_UP_CANCELED_FROZEN:
371 case CPU_DEAD:
372 case CPU_DEAD_FROZEN:
373 if (prof_cpu_mask != NULL)
374 cpumask_clear_cpu(cpu, prof_cpu_mask);
375 if (per_cpu(cpu_profile_hits, cpu)[0]) {
376 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
377 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
378 __free_page(page);
379 }
380 if (per_cpu(cpu_profile_hits, cpu)[1]) {
381 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
382 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
383 __free_page(page);
384 }
385 break;
386 }
387 return NOTIFY_OK;
388 }
389 #else /* !CONFIG_SMP */
390 #define profile_flip_buffers() do { } while (0)
391 #define profile_discard_flip_buffers() do { } while (0)
392 #define profile_cpu_callback NULL
393
do_profile_hits(int type,void * __pc,unsigned int nr_hits)394 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
395 {
396 unsigned long pc;
397 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
398 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
399 }
400 #endif /* !CONFIG_SMP */
401
profile_hits(int type,void * __pc,unsigned int nr_hits)402 void profile_hits(int type, void *__pc, unsigned int nr_hits)
403 {
404 if (prof_on != type || !prof_buffer)
405 return;
406 do_profile_hits(type, __pc, nr_hits);
407 }
408 EXPORT_SYMBOL_GPL(profile_hits);
409
profile_tick(int type)410 void profile_tick(int type)
411 {
412 struct pt_regs *regs = get_irq_regs();
413
414 if (!user_mode(regs) && prof_cpu_mask != NULL &&
415 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
416 profile_hit(type, (void *)profile_pc(regs));
417 }
418
419 #ifdef CONFIG_PROC_FS
420 #include <linux/proc_fs.h>
421 #include <linux/seq_file.h>
422 #include <asm/uaccess.h>
423
prof_cpu_mask_proc_show(struct seq_file * m,void * v)424 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
425 {
426 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
427 return 0;
428 }
429
prof_cpu_mask_proc_open(struct inode * inode,struct file * file)430 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
431 {
432 return single_open(file, prof_cpu_mask_proc_show, NULL);
433 }
434
prof_cpu_mask_proc_write(struct file * file,const char __user * buffer,size_t count,loff_t * pos)435 static ssize_t prof_cpu_mask_proc_write(struct file *file,
436 const char __user *buffer, size_t count, loff_t *pos)
437 {
438 cpumask_var_t new_value;
439 int err;
440
441 if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
442 return -ENOMEM;
443
444 err = cpumask_parse_user(buffer, count, new_value);
445 if (!err) {
446 cpumask_copy(prof_cpu_mask, new_value);
447 err = count;
448 }
449 free_cpumask_var(new_value);
450 return err;
451 }
452
453 static const struct file_operations prof_cpu_mask_proc_fops = {
454 .open = prof_cpu_mask_proc_open,
455 .read = seq_read,
456 .llseek = seq_lseek,
457 .release = single_release,
458 .write = prof_cpu_mask_proc_write,
459 };
460
create_prof_cpu_mask(void)461 void create_prof_cpu_mask(void)
462 {
463 /* create /proc/irq/prof_cpu_mask */
464 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
465 }
466
467 /*
468 * This function accesses profiling information. The returned data is
469 * binary: the sampling step and the actual contents of the profile
470 * buffer. Use of the program readprofile is recommended in order to
471 * get meaningful info out of these data.
472 */
473 static ssize_t
read_profile(struct file * file,char __user * buf,size_t count,loff_t * ppos)474 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
475 {
476 unsigned long p = *ppos;
477 ssize_t read;
478 char *pnt;
479 unsigned long sample_step = 1UL << prof_shift;
480
481 profile_flip_buffers();
482 if (p >= (prof_len+1)*sizeof(unsigned int))
483 return 0;
484 if (count > (prof_len+1)*sizeof(unsigned int) - p)
485 count = (prof_len+1)*sizeof(unsigned int) - p;
486 read = 0;
487
488 while (p < sizeof(unsigned int) && count > 0) {
489 if (put_user(*((char *)(&sample_step)+p), buf))
490 return -EFAULT;
491 buf++; p++; count--; read++;
492 }
493 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
494 if (copy_to_user(buf, (void *)pnt, count))
495 return -EFAULT;
496 read += count;
497 *ppos += read;
498 return read;
499 }
500
501 /*
502 * Writing to /proc/profile resets the counters
503 *
504 * Writing a 'profiling multiplier' value into it also re-sets the profiling
505 * interrupt frequency, on architectures that support this.
506 */
write_profile(struct file * file,const char __user * buf,size_t count,loff_t * ppos)507 static ssize_t write_profile(struct file *file, const char __user *buf,
508 size_t count, loff_t *ppos)
509 {
510 #ifdef CONFIG_SMP
511 extern int setup_profiling_timer(unsigned int multiplier);
512
513 if (count == sizeof(int)) {
514 unsigned int multiplier;
515
516 if (copy_from_user(&multiplier, buf, sizeof(int)))
517 return -EFAULT;
518
519 if (setup_profiling_timer(multiplier))
520 return -EINVAL;
521 }
522 #endif
523 profile_discard_flip_buffers();
524 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
525 return count;
526 }
527
528 static const struct file_operations proc_profile_operations = {
529 .read = read_profile,
530 .write = write_profile,
531 .llseek = default_llseek,
532 };
533
534 #ifdef CONFIG_SMP
profile_nop(void * unused)535 static void profile_nop(void *unused)
536 {
537 }
538
create_hash_tables(void)539 static int create_hash_tables(void)
540 {
541 int cpu;
542
543 for_each_online_cpu(cpu) {
544 int node = cpu_to_mem(cpu);
545 struct page *page;
546
547 page = __alloc_pages_node(node,
548 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
549 0);
550 if (!page)
551 goto out_cleanup;
552 per_cpu(cpu_profile_hits, cpu)[1]
553 = (struct profile_hit *)page_address(page);
554 page = __alloc_pages_node(node,
555 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
556 0);
557 if (!page)
558 goto out_cleanup;
559 per_cpu(cpu_profile_hits, cpu)[0]
560 = (struct profile_hit *)page_address(page);
561 }
562 return 0;
563 out_cleanup:
564 prof_on = 0;
565 smp_mb();
566 on_each_cpu(profile_nop, NULL, 1);
567 for_each_online_cpu(cpu) {
568 struct page *page;
569
570 if (per_cpu(cpu_profile_hits, cpu)[0]) {
571 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
572 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
573 __free_page(page);
574 }
575 if (per_cpu(cpu_profile_hits, cpu)[1]) {
576 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
577 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
578 __free_page(page);
579 }
580 }
581 return -1;
582 }
583 #else
584 #define create_hash_tables() ({ 0; })
585 #endif
586
create_proc_profile(void)587 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
588 {
589 struct proc_dir_entry *entry;
590 int err = 0;
591
592 if (!prof_on)
593 return 0;
594
595 cpu_notifier_register_begin();
596
597 if (create_hash_tables()) {
598 err = -ENOMEM;
599 goto out;
600 }
601
602 entry = proc_create("profile", S_IWUSR | S_IRUGO,
603 NULL, &proc_profile_operations);
604 if (!entry)
605 goto out;
606 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
607 __hotcpu_notifier(profile_cpu_callback, 0);
608
609 out:
610 cpu_notifier_register_done();
611 return err;
612 }
613 subsys_initcall(create_proc_profile);
614 #endif /* CONFIG_PROC_FS */
615