projects/linux·blob v3.10-rc2 · refs

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