xref: /openbmc/linux/kernel/profile.c (revision 22246614)
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  *	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
14  */
15 
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>
28 
29 struct profile_hit {
30 	u32 pc, hits;
31 };
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)
36 
37 /* Oprofile timer tick hook */
38 static int (*timer_hook)(struct pt_regs *) __read_mostly;
39 
40 static atomic_t *prof_buffer;
41 static unsigned long prof_len, prof_shift;
42 
43 int prof_on __read_mostly;
44 EXPORT_SYMBOL_GPL(prof_on);
45 
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 */
52 
53 static int __init profile_setup(char *str)
54 {
55 	static char __initdata schedstr[] = "schedule";
56 	static char __initdata sleepstr[] = "sleep";
57 	static char __initdata 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 
103 void __init profile_init(void)
104 {
105 	if (!prof_on)
106 		return;
107 
108 	/* only text is profiled */
109 	prof_len = (_etext - _stext) >> prof_shift;
110 	prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
111 }
112 
113 /* Profile event notifications */
114 
115 #ifdef CONFIG_PROFILING
116 
117 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
118 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
119 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
120 
121 void profile_task_exit(struct task_struct *task)
122 {
123 	blocking_notifier_call_chain(&task_exit_notifier, 0, task);
124 }
125 
126 int profile_handoff_task(struct task_struct *task)
127 {
128 	int ret;
129 	ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
130 	return (ret == NOTIFY_OK) ? 1 : 0;
131 }
132 
133 void profile_munmap(unsigned long addr)
134 {
135 	blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
136 }
137 
138 int task_handoff_register(struct notifier_block *n)
139 {
140 	return atomic_notifier_chain_register(&task_free_notifier, n);
141 }
142 EXPORT_SYMBOL_GPL(task_handoff_register);
143 
144 int task_handoff_unregister(struct notifier_block *n)
145 {
146 	return atomic_notifier_chain_unregister(&task_free_notifier, n);
147 }
148 EXPORT_SYMBOL_GPL(task_handoff_unregister);
149 
150 int profile_event_register(enum profile_type type, struct notifier_block *n)
151 {
152 	int err = -EINVAL;
153 
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;
163 	}
164 
165 	return err;
166 }
167 EXPORT_SYMBOL_GPL(profile_event_register);
168 
169 int profile_event_unregister(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_unregister(
176 				&task_exit_notifier, n);
177 		break;
178 	case PROFILE_MUNMAP:
179 		err = blocking_notifier_chain_unregister(
180 				&munmap_notifier, n);
181 		break;
182 	}
183 
184 	return err;
185 }
186 EXPORT_SYMBOL_GPL(profile_event_unregister);
187 
188 int register_timer_hook(int (*hook)(struct pt_regs *))
189 {
190 	if (timer_hook)
191 		return -EBUSY;
192 	timer_hook = hook;
193 	return 0;
194 }
195 EXPORT_SYMBOL_GPL(register_timer_hook);
196 
197 void unregister_timer_hook(int (*hook)(struct pt_regs *))
198 {
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. */
203 }
204 EXPORT_SYMBOL_GPL(unregister_timer_hook);
205 
206 #endif /* CONFIG_PROFILING */
207 
208 
209 #ifdef CONFIG_SMP
210 /*
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.
219  *
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.
238  *
239  * -- wli
240  */
241 static void __profile_flip_buffers(void *unused)
242 {
243 	int cpu = smp_processor_id();
244 
245 	per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
246 }
247 
248 static void profile_flip_buffers(void)
249 {
250 	int i, j, cpu;
251 
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;
263 			}
264 			atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
265 			hits[i].hits = hits[i].pc = 0;
266 		}
267 	}
268 	mutex_unlock(&profile_flip_mutex);
269 }
270 
271 static void profile_discard_flip_buffers(void)
272 {
273 	int i, cpu;
274 
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));
282 	}
283 	mutex_unlock(&profile_flip_mutex);
284 }
285 
286 void profile_hits(int type, void *__pc, unsigned int nr_hits)
287 {
288 	unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
289 	int i, j, cpu;
290 	struct profile_hit *hits;
291 
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;
302 	}
303 	/*
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:
307 	 */
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;
318 			}
319 		}
320 		i = (i + secondary) & (NR_PROFILE_HIT - 1);
321 	} while (i != primary);
322 
323 	/*
324 	 * Add the current hit(s) and flush the write-queue out
325 	 * to the global buffer:
326 	 */
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;
331 	}
332 out:
333 	local_irq_restore(flags);
334 	put_cpu();
335 }
336 
337 static int __devinit profile_cpu_callback(struct notifier_block *info,
338 					unsigned long action, void *__cpu)
339 {
340 	int node, cpu = (unsigned long)__cpu;
341 	struct page *page;
342 
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,
351 					0);
352 			if (!page)
353 				return NOTIFY_BAD;
354 			per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
355 		}
356 		if (!per_cpu(cpu_profile_hits, cpu)[0]) {
357 			page = alloc_pages_node(node,
358 					GFP_KERNEL | __GFP_ZERO,
359 					0);
360 			if (!page)
361 				goto out_free;
362 			per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
363 		}
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);
383 		}
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);
388 		}
389 		break;
390 	}
391 	return NOTIFY_OK;
392 }
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
397 
398 void profile_hits(int type, void *__pc, unsigned int nr_hits)
399 {
400 	unsigned long pc;
401 
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)]);
406 }
407 #endif /* !CONFIG_SMP */
408 EXPORT_SYMBOL_GPL(profile_hits);
409 
410 void profile_tick(int type)
411 {
412 	struct pt_regs *regs = get_irq_regs();
413 
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));
418 }
419 
420 #ifdef CONFIG_PROC_FS
421 #include <linux/proc_fs.h>
422 #include <asm/uaccess.h>
423 #include <asm/ptrace.h>
424 
425 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
426 			int count, int *eof, void *data)
427 {
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;
433 }
434 
435 static int prof_cpu_mask_write_proc(struct file *file,
436 	const char __user *buffer,  unsigned long count, void *data)
437 {
438 	cpumask_t *mask = (cpumask_t *)data;
439 	unsigned long full_count = count, err;
440 	cpumask_t new_value;
441 
442 	err = cpumask_parse_user(buffer, count, new_value);
443 	if (err)
444 		return err;
445 
446 	*mask = new_value;
447 	return full_count;
448 }
449 
450 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
451 {
452 	struct proc_dir_entry *entry;
453 
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;
461 }
462 
463 /*
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.
468  */
469 static ssize_t
470 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
471 {
472 	unsigned long p = *ppos;
473 	ssize_t read;
474 	char *pnt;
475 	unsigned int sample_step = 1 << prof_shift;
476 
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;
483 
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++;
488 	}
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;
495 }
496 
497 /*
498  * Writing to /proc/profile resets the counters
499  *
500  * Writing a 'profiling multiplier' value into it also re-sets the profiling
501  * interrupt frequency, on architectures that support this.
502  */
503 static ssize_t write_profile(struct file *file, const char __user *buf,
504 			     size_t count, loff_t *ppos)
505 {
506 #ifdef CONFIG_SMP
507 	extern int setup_profiling_timer(unsigned int multiplier);
508 
509 	if (count == sizeof(int)) {
510 		unsigned int multiplier;
511 
512 		if (copy_from_user(&multiplier, buf, sizeof(int)))
513 			return -EFAULT;
514 
515 		if (setup_profiling_timer(multiplier))
516 			return -EINVAL;
517 	}
518 #endif
519 	profile_discard_flip_buffers();
520 	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
521 	return count;
522 }
523 
524 static const struct file_operations proc_profile_operations = {
525 	.read		= read_profile,
526 	.write		= write_profile,
527 };
528 
529 #ifdef CONFIG_SMP
530 static void __init profile_nop(void *unused)
531 {
532 }
533 
534 static int __init create_hash_tables(void)
535 {
536 	int cpu;
537 
538 	for_each_online_cpu(cpu) {
539 		int node = cpu_to_node(cpu);
540 		struct page *page;
541 
542 		page = alloc_pages_node(node,
543 				GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
544 				0);
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,
551 				0);
552 		if (!page)
553 			goto out_cleanup;
554 		per_cpu(cpu_profile_hits, cpu)[0]
555 				= (struct profile_hit *)page_address(page);
556 	}
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;
564 
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);
569 		}
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);
574 		}
575 	}
576 	return -1;
577 }
578 #else
579 #define create_hash_tables()			({ 0; })
580 #endif
581 
582 static int __init create_proc_profile(void)
583 {
584 	struct proc_dir_entry *entry;
585 
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;
597 }
598 module_init(create_proc_profile);
599 #endif /* CONFIG_PROC_FS */
600