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[linux-2.6/sactl.git] / kernel / profile.c
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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.
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 * William Irwin, Oracle, July 2004
12 * Amortized hit count accounting via per-cpu open-addressed hashtables
13 * to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
16 #include <linux/module.h>
17 #include <linux/profile.h>
18 #include <linux/bootmem.h>
19 #include <linux/notifier.h>
20 #include <linux/mm.h>
21 #include <linux/cpumask.h>
22 #include <linux/cpu.h>
23 #include <linux/highmem.h>
24 #include <linux/mutex.h>
25 #include <asm/sections.h>
26 #include <asm/irq_regs.h>
27 #include <asm/ptrace.h>
29 struct profile_hit {
30 u32 pc, hits;
32 #define PROFILE_GRPSHIFT 3
33 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
34 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
35 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
37 /* Oprofile timer tick hook */
38 static int (*timer_hook)(struct pt_regs *) __read_mostly;
40 static atomic_t *prof_buffer;
41 static unsigned long prof_len, prof_shift;
43 int prof_on __read_mostly;
44 EXPORT_SYMBOL_GPL(prof_on);
46 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
47 #ifdef CONFIG_SMP
48 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
49 static DEFINE_PER_CPU(int, cpu_profile_flip);
50 static DEFINE_MUTEX(profile_flip_mutex);
51 #endif /* CONFIG_SMP */
53 static int __init profile_setup(char *str)
55 static char __initdata schedstr[] = "schedule";
56 static char __initdata sleepstr[] = "sleep";
57 static char __initdata kvmstr[] = "kvm";
58 int par;
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);
98 return 1;
100 __setup("profile=", profile_setup);
103 void __init profile_init(void)
105 if (!prof_on)
106 return;
108 /* only text is profiled */
109 prof_len = (_etext - _stext) >> prof_shift;
110 prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
113 /* Profile event notifications */
115 #ifdef CONFIG_PROFILING
117 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
118 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
119 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
121 void profile_task_exit(struct task_struct *task)
123 blocking_notifier_call_chain(&task_exit_notifier, 0, task);
126 int profile_handoff_task(struct task_struct *task)
128 int ret;
129 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
130 return (ret == NOTIFY_OK) ? 1 : 0;
133 void profile_munmap(unsigned long addr)
135 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
138 int task_handoff_register(struct notifier_block *n)
140 return atomic_notifier_chain_register(&task_free_notifier, n);
142 EXPORT_SYMBOL_GPL(task_handoff_register);
144 int task_handoff_unregister(struct notifier_block *n)
146 return atomic_notifier_chain_unregister(&task_free_notifier, n);
148 EXPORT_SYMBOL_GPL(task_handoff_unregister);
150 int profile_event_register(enum profile_type type, struct notifier_block *n)
152 int err = -EINVAL;
154 switch (type) {
155 case PROFILE_TASK_EXIT:
156 err = blocking_notifier_chain_register(
157 &task_exit_notifier, n);
158 break;
159 case PROFILE_MUNMAP:
160 err = blocking_notifier_chain_register(
161 &munmap_notifier, n);
162 break;
165 return err;
167 EXPORT_SYMBOL_GPL(profile_event_register);
169 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
171 int err = -EINVAL;
173 switch (type) {
174 case PROFILE_TASK_EXIT:
175 err = blocking_notifier_chain_unregister(
176 &task_exit_notifier, n);
177 break;
178 case PROFILE_MUNMAP:
179 err = blocking_notifier_chain_unregister(
180 &munmap_notifier, n);
181 break;
184 return err;
186 EXPORT_SYMBOL_GPL(profile_event_unregister);
188 int register_timer_hook(int (*hook)(struct pt_regs *))
190 if (timer_hook)
191 return -EBUSY;
192 timer_hook = hook;
193 return 0;
195 EXPORT_SYMBOL_GPL(register_timer_hook);
197 void unregister_timer_hook(int (*hook)(struct pt_regs *))
199 WARN_ON(hook != timer_hook);
200 timer_hook = NULL;
201 /* make sure all CPUs see the NULL hook */
202 synchronize_sched(); /* Allow ongoing interrupts to complete. */
204 EXPORT_SYMBOL_GPL(unregister_timer_hook);
206 #endif /* CONFIG_PROFILING */
209 #ifdef CONFIG_SMP
211 * Each cpu has a pair of open-addressed hashtables for pending
212 * profile hits. read_profile() IPI's all cpus to request them
213 * to flip buffers and flushes their contents to prof_buffer itself.
214 * Flip requests are serialized by the profile_flip_mutex. The sole
215 * use of having a second hashtable is for avoiding cacheline
216 * contention that would otherwise happen during flushes of pending
217 * profile hits required for the accuracy of reported profile hits
218 * and so resurrect the interrupt livelock issue.
220 * The open-addressed hashtables are indexed by profile buffer slot
221 * and hold the number of pending hits to that profile buffer slot on
222 * a cpu in an entry. When the hashtable overflows, all pending hits
223 * are accounted to their corresponding profile buffer slots with
224 * atomic_add() and the hashtable emptied. As numerous pending hits
225 * may be accounted to a profile buffer slot in a hashtable entry,
226 * this amortizes a number of atomic profile buffer increments likely
227 * to be far larger than the number of entries in the hashtable,
228 * particularly given that the number of distinct profile buffer
229 * positions to which hits are accounted during short intervals (e.g.
230 * several seconds) is usually very small. Exclusion from buffer
231 * flipping is provided by interrupt disablement (note that for
232 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
233 * process context).
234 * The hash function is meant to be lightweight as opposed to strong,
235 * and was vaguely inspired by ppc64 firmware-supported inverted
236 * pagetable hash functions, but uses a full hashtable full of finite
237 * collision chains, not just pairs of them.
239 * -- wli
241 static void __profile_flip_buffers(void *unused)
243 int cpu = smp_processor_id();
245 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
248 static void profile_flip_buffers(void)
250 int i, j, cpu;
252 mutex_lock(&profile_flip_mutex);
253 j = per_cpu(cpu_profile_flip, get_cpu());
254 put_cpu();
255 on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
256 for_each_online_cpu(cpu) {
257 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
258 for (i = 0; i < NR_PROFILE_HIT; ++i) {
259 if (!hits[i].hits) {
260 if (hits[i].pc)
261 hits[i].pc = 0;
262 continue;
264 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
265 hits[i].hits = hits[i].pc = 0;
268 mutex_unlock(&profile_flip_mutex);
271 static void profile_discard_flip_buffers(void)
273 int i, cpu;
275 mutex_lock(&profile_flip_mutex);
276 i = per_cpu(cpu_profile_flip, get_cpu());
277 put_cpu();
278 on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
279 for_each_online_cpu(cpu) {
280 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
281 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
283 mutex_unlock(&profile_flip_mutex);
286 void profile_hits(int type, void *__pc, unsigned int nr_hits)
288 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
289 int i, j, cpu;
290 struct profile_hit *hits;
292 if (prof_on != type || !prof_buffer)
293 return;
294 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
295 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
296 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
297 cpu = get_cpu();
298 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
299 if (!hits) {
300 put_cpu();
301 return;
304 * We buffer the global profiler buffer into a per-CPU
305 * queue and thus reduce the number of global (and possibly
306 * NUMA-alien) accesses. The write-queue is self-coalescing:
308 local_irq_save(flags);
309 do {
310 for (j = 0; j < PROFILE_GRPSZ; ++j) {
311 if (hits[i + j].pc == pc) {
312 hits[i + j].hits += nr_hits;
313 goto out;
314 } else if (!hits[i + j].hits) {
315 hits[i + j].pc = pc;
316 hits[i + j].hits = nr_hits;
317 goto out;
320 i = (i + secondary) & (NR_PROFILE_HIT - 1);
321 } while (i != primary);
324 * Add the current hit(s) and flush the write-queue out
325 * to the global buffer:
327 atomic_add(nr_hits, &prof_buffer[pc]);
328 for (i = 0; i < NR_PROFILE_HIT; ++i) {
329 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
330 hits[i].pc = hits[i].hits = 0;
332 out:
333 local_irq_restore(flags);
334 put_cpu();
337 static int __devinit profile_cpu_callback(struct notifier_block *info,
338 unsigned long action, void *__cpu)
340 int node, cpu = (unsigned long)__cpu;
341 struct page *page;
343 switch (action) {
344 case CPU_UP_PREPARE:
345 case CPU_UP_PREPARE_FROZEN:
346 node = cpu_to_node(cpu);
347 per_cpu(cpu_profile_flip, cpu) = 0;
348 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
349 page = alloc_pages_node(node,
350 GFP_KERNEL | __GFP_ZERO,
352 if (!page)
353 return NOTIFY_BAD;
354 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
356 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
357 page = alloc_pages_node(node,
358 GFP_KERNEL | __GFP_ZERO,
360 if (!page)
361 goto out_free;
362 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
364 break;
365 out_free:
366 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
367 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
368 __free_page(page);
369 return NOTIFY_BAD;
370 case CPU_ONLINE:
371 case CPU_ONLINE_FROZEN:
372 cpu_set(cpu, prof_cpu_mask);
373 break;
374 case CPU_UP_CANCELED:
375 case CPU_UP_CANCELED_FROZEN:
376 case CPU_DEAD:
377 case CPU_DEAD_FROZEN:
378 cpu_clear(cpu, prof_cpu_mask);
379 if (per_cpu(cpu_profile_hits, cpu)[0]) {
380 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
381 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
382 __free_page(page);
384 if (per_cpu(cpu_profile_hits, cpu)[1]) {
385 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
386 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
387 __free_page(page);
389 break;
391 return NOTIFY_OK;
393 #else /* !CONFIG_SMP */
394 #define profile_flip_buffers() do { } while (0)
395 #define profile_discard_flip_buffers() do { } while (0)
396 #define profile_cpu_callback NULL
398 void profile_hits(int type, void *__pc, unsigned int nr_hits)
400 unsigned long pc;
402 if (prof_on != type || !prof_buffer)
403 return;
404 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
405 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
407 #endif /* !CONFIG_SMP */
408 EXPORT_SYMBOL_GPL(profile_hits);
410 void profile_tick(int type)
412 struct pt_regs *regs = get_irq_regs();
414 if (type == CPU_PROFILING && timer_hook)
415 timer_hook(regs);
416 if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
417 profile_hit(type, (void *)profile_pc(regs));
420 #ifdef CONFIG_PROC_FS
421 #include <linux/proc_fs.h>
422 #include <asm/uaccess.h>
423 #include <asm/ptrace.h>
425 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
426 int count, int *eof, void *data)
428 int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
429 if (count - len < 2)
430 return -EINVAL;
431 len += sprintf(page + len, "\n");
432 return len;
435 static int prof_cpu_mask_write_proc(struct file *file,
436 const char __user *buffer, unsigned long count, void *data)
438 cpumask_t *mask = (cpumask_t *)data;
439 unsigned long full_count = count, err;
440 cpumask_t new_value;
442 err = cpumask_parse_user(buffer, count, new_value);
443 if (err)
444 return err;
446 *mask = new_value;
447 return full_count;
450 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
452 struct proc_dir_entry *entry;
454 /* create /proc/irq/prof_cpu_mask */
455 entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
456 if (!entry)
457 return;
458 entry->data = (void *)&prof_cpu_mask;
459 entry->read_proc = prof_cpu_mask_read_proc;
460 entry->write_proc = prof_cpu_mask_write_proc;
464 * This function accesses profiling information. The returned data is
465 * binary: the sampling step and the actual contents of the profile
466 * buffer. Use of the program readprofile is recommended in order to
467 * get meaningful info out of these data.
469 static ssize_t
470 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
472 unsigned long p = *ppos;
473 ssize_t read;
474 char *pnt;
475 unsigned int sample_step = 1 << prof_shift;
477 profile_flip_buffers();
478 if (p >= (prof_len+1)*sizeof(unsigned int))
479 return 0;
480 if (count > (prof_len+1)*sizeof(unsigned int) - p)
481 count = (prof_len+1)*sizeof(unsigned int) - p;
482 read = 0;
484 while (p < sizeof(unsigned int) && count > 0) {
485 if (put_user(*((char *)(&sample_step)+p), buf))
486 return -EFAULT;
487 buf++; p++; count--; read++;
489 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
490 if (copy_to_user(buf, (void *)pnt, count))
491 return -EFAULT;
492 read += count;
493 *ppos += read;
494 return read;
498 * Writing to /proc/profile resets the counters
500 * Writing a 'profiling multiplier' value into it also re-sets the profiling
501 * interrupt frequency, on architectures that support this.
503 static ssize_t write_profile(struct file *file, const char __user *buf,
504 size_t count, loff_t *ppos)
506 #ifdef CONFIG_SMP
507 extern int setup_profiling_timer(unsigned int multiplier);
509 if (count == sizeof(int)) {
510 unsigned int multiplier;
512 if (copy_from_user(&multiplier, buf, sizeof(int)))
513 return -EFAULT;
515 if (setup_profiling_timer(multiplier))
516 return -EINVAL;
518 #endif
519 profile_discard_flip_buffers();
520 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
521 return count;
524 static const struct file_operations proc_profile_operations = {
525 .read = read_profile,
526 .write = write_profile,
529 #ifdef CONFIG_SMP
530 static void __init profile_nop(void *unused)
534 static int __init create_hash_tables(void)
536 int cpu;
538 for_each_online_cpu(cpu) {
539 int node = cpu_to_node(cpu);
540 struct page *page;
542 page = alloc_pages_node(node,
543 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
545 if (!page)
546 goto out_cleanup;
547 per_cpu(cpu_profile_hits, cpu)[1]
548 = (struct profile_hit *)page_address(page);
549 page = alloc_pages_node(node,
550 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
552 if (!page)
553 goto out_cleanup;
554 per_cpu(cpu_profile_hits, cpu)[0]
555 = (struct profile_hit *)page_address(page);
557 return 0;
558 out_cleanup:
559 prof_on = 0;
560 smp_mb();
561 on_each_cpu(profile_nop, NULL, 0, 1);
562 for_each_online_cpu(cpu) {
563 struct page *page;
565 if (per_cpu(cpu_profile_hits, cpu)[0]) {
566 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
567 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
568 __free_page(page);
570 if (per_cpu(cpu_profile_hits, cpu)[1]) {
571 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
572 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
573 __free_page(page);
576 return -1;
578 #else
579 #define create_hash_tables() ({ 0; })
580 #endif
582 static int __init create_proc_profile(void)
584 struct proc_dir_entry *entry;
586 if (!prof_on)
587 return 0;
588 if (create_hash_tables())
589 return -1;
590 entry = proc_create("profile", S_IWUSR | S_IRUGO,
591 NULL, &proc_profile_operations);
592 if (!entry)
593 return 0;
594 entry->size = (1+prof_len) * sizeof(atomic_t);
595 hotcpu_notifier(profile_cpu_callback, 0);
596 return 0;
598 module_init(create_proc_profile);
599 #endif /* CONFIG_PROC_FS */