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,
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,
17 #include <linux/export.h>
18 #include <linux/profile.h>
19 #include <linux/bootmem.h>
20 #include <linux/notifier.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>
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)
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_var_t prof_cpu_mask;
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 int profile_setup(char *str)
55 static const char schedstr[] = "schedule";
56 static const char sleepstr[] = "sleep";
57 static const char kvmstr[] = "kvm";
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))
67 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
70 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
71 #endif /* CONFIG_SCHEDSTATS */
72 } else if (!strncmp(str, schedstr, strlen(schedstr))) {
73 prof_on = SCHED_PROFILING;
74 if (str[strlen(schedstr)] == ',')
75 str += strlen(schedstr) + 1;
76 if (get_option(&str, &par))
78 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
80 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
81 prof_on = KVM_PROFILING;
82 if (str[strlen(kvmstr)] == ',')
83 str += strlen(kvmstr) + 1;
84 if (get_option(&str, &par))
86 pr_info("kernel KVM profiling enabled (shift: %ld)\n",
88 } else if (get_option(&str, &par)) {
90 prof_on = CPU_PROFILING;
91 pr_info("kernel profiling enabled (shift: %ld)\n",
96 __setup("profile=", profile_setup);
99 int __ref profile_init(void)
105 /* only text is profiled */
106 prof_len = (_etext - _stext) >> prof_shift;
107 buffer_bytes = prof_len*sizeof(atomic_t);
109 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
112 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
114 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
118 prof_buffer = alloc_pages_exact(buffer_bytes,
119 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
123 prof_buffer = vzalloc(buffer_bytes);
127 free_cpumask_var(prof_cpu_mask);
131 /* Profile event notifications */
133 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
134 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
135 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
137 void profile_task_exit(struct task_struct *task)
139 blocking_notifier_call_chain(&task_exit_notifier, 0, task);
142 int profile_handoff_task(struct task_struct *task)
145 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
146 return (ret == NOTIFY_OK) ? 1 : 0;
149 void profile_munmap(unsigned long addr)
151 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
154 int task_handoff_register(struct notifier_block *n)
156 return atomic_notifier_chain_register(&task_free_notifier, n);
158 EXPORT_SYMBOL_GPL(task_handoff_register);
160 int task_handoff_unregister(struct notifier_block *n)
162 return atomic_notifier_chain_unregister(&task_free_notifier, n);
164 EXPORT_SYMBOL_GPL(task_handoff_unregister);
166 int profile_event_register(enum profile_type type, struct notifier_block *n)
171 case PROFILE_TASK_EXIT:
172 err = blocking_notifier_chain_register(
173 &task_exit_notifier, n);
176 err = blocking_notifier_chain_register(
177 &munmap_notifier, n);
183 EXPORT_SYMBOL_GPL(profile_event_register);
185 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
190 case PROFILE_TASK_EXIT:
191 err = blocking_notifier_chain_unregister(
192 &task_exit_notifier, n);
195 err = blocking_notifier_chain_unregister(
196 &munmap_notifier, n);
202 EXPORT_SYMBOL_GPL(profile_event_unregister);
206 * Each cpu has a pair of open-addressed hashtables for pending
207 * profile hits. read_profile() IPI's all cpus to request them
208 * to flip buffers and flushes their contents to prof_buffer itself.
209 * Flip requests are serialized by the profile_flip_mutex. The sole
210 * use of having a second hashtable is for avoiding cacheline
211 * contention that would otherwise happen during flushes of pending
212 * profile hits required for the accuracy of reported profile hits
213 * and so resurrect the interrupt livelock issue.
215 * The open-addressed hashtables are indexed by profile buffer slot
216 * and hold the number of pending hits to that profile buffer slot on
217 * a cpu in an entry. When the hashtable overflows, all pending hits
218 * are accounted to their corresponding profile buffer slots with
219 * atomic_add() and the hashtable emptied. As numerous pending hits
220 * may be accounted to a profile buffer slot in a hashtable entry,
221 * this amortizes a number of atomic profile buffer increments likely
222 * to be far larger than the number of entries in the hashtable,
223 * particularly given that the number of distinct profile buffer
224 * positions to which hits are accounted during short intervals (e.g.
225 * several seconds) is usually very small. Exclusion from buffer
226 * flipping is provided by interrupt disablement (note that for
227 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
229 * The hash function is meant to be lightweight as opposed to strong,
230 * and was vaguely inspired by ppc64 firmware-supported inverted
231 * pagetable hash functions, but uses a full hashtable full of finite
232 * collision chains, not just pairs of them.
236 static void __profile_flip_buffers(void *unused)
238 int cpu = smp_processor_id();
240 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
243 static void profile_flip_buffers(void)
247 mutex_lock(&profile_flip_mutex);
248 j = per_cpu(cpu_profile_flip, get_cpu());
250 on_each_cpu(__profile_flip_buffers, NULL, 1);
251 for_each_online_cpu(cpu) {
252 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
253 for (i = 0; i < NR_PROFILE_HIT; ++i) {
259 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
260 hits[i].hits = hits[i].pc = 0;
263 mutex_unlock(&profile_flip_mutex);
266 static void profile_discard_flip_buffers(void)
270 mutex_lock(&profile_flip_mutex);
271 i = per_cpu(cpu_profile_flip, get_cpu());
273 on_each_cpu(__profile_flip_buffers, NULL, 1);
274 for_each_online_cpu(cpu) {
275 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
276 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
278 mutex_unlock(&profile_flip_mutex);
281 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
283 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
285 struct profile_hit *hits;
287 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
288 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
289 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
291 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
297 * We buffer the global profiler buffer into a per-CPU
298 * queue and thus reduce the number of global (and possibly
299 * NUMA-alien) accesses. The write-queue is self-coalescing:
301 local_irq_save(flags);
303 for (j = 0; j < PROFILE_GRPSZ; ++j) {
304 if (hits[i + j].pc == pc) {
305 hits[i + j].hits += nr_hits;
307 } else if (!hits[i + j].hits) {
309 hits[i + j].hits = nr_hits;
313 i = (i + secondary) & (NR_PROFILE_HIT - 1);
314 } while (i != primary);
317 * Add the current hit(s) and flush the write-queue out
318 * to the global buffer:
320 atomic_add(nr_hits, &prof_buffer[pc]);
321 for (i = 0; i < NR_PROFILE_HIT; ++i) {
322 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
323 hits[i].pc = hits[i].hits = 0;
326 local_irq_restore(flags);
330 static int profile_cpu_callback(struct notifier_block *info,
331 unsigned long action, void *__cpu)
333 int node, cpu = (unsigned long)__cpu;
338 case CPU_UP_PREPARE_FROZEN:
339 node = cpu_to_mem(cpu);
340 per_cpu(cpu_profile_flip, cpu) = 0;
341 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
342 page = __alloc_pages_node(node,
343 GFP_KERNEL | __GFP_ZERO,
346 return notifier_from_errno(-ENOMEM);
347 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
349 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
350 page = __alloc_pages_node(node,
351 GFP_KERNEL | __GFP_ZERO,
355 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
359 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
360 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
362 return notifier_from_errno(-ENOMEM);
364 case CPU_ONLINE_FROZEN:
365 if (prof_cpu_mask != NULL)
366 cpumask_set_cpu(cpu, prof_cpu_mask);
368 case CPU_UP_CANCELED:
369 case CPU_UP_CANCELED_FROZEN:
371 case CPU_DEAD_FROZEN:
372 if (prof_cpu_mask != NULL)
373 cpumask_clear_cpu(cpu, prof_cpu_mask);
374 if (per_cpu(cpu_profile_hits, cpu)[0]) {
375 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
376 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
379 if (per_cpu(cpu_profile_hits, cpu)[1]) {
380 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
381 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
388 #else /* !CONFIG_SMP */
389 #define profile_flip_buffers() do { } while (0)
390 #define profile_discard_flip_buffers() do { } while (0)
391 #define profile_cpu_callback NULL
393 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
396 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
397 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
399 #endif /* !CONFIG_SMP */
401 void profile_hits(int type, void *__pc, unsigned int nr_hits)
403 if (prof_on != type || !prof_buffer)
405 do_profile_hits(type, __pc, nr_hits);
407 EXPORT_SYMBOL_GPL(profile_hits);
409 void profile_tick(int type)
411 struct pt_regs *regs = get_irq_regs();
413 if (!user_mode(regs) && prof_cpu_mask != NULL &&
414 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
415 profile_hit(type, (void *)profile_pc(regs));
418 #ifdef CONFIG_PROC_FS
419 #include <linux/proc_fs.h>
420 #include <linux/seq_file.h>
421 #include <asm/uaccess.h>
423 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
425 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
429 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
431 return single_open(file, prof_cpu_mask_proc_show, NULL);
434 static ssize_t prof_cpu_mask_proc_write(struct file *file,
435 const char __user *buffer, size_t count, loff_t *pos)
437 cpumask_var_t new_value;
440 if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
443 err = cpumask_parse_user(buffer, count, new_value);
445 cpumask_copy(prof_cpu_mask, new_value);
448 free_cpumask_var(new_value);
452 static const struct file_operations prof_cpu_mask_proc_fops = {
453 .open = prof_cpu_mask_proc_open,
456 .release = single_release,
457 .write = prof_cpu_mask_proc_write,
460 void create_prof_cpu_mask(void)
462 /* create /proc/irq/prof_cpu_mask */
463 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
467 * This function accesses profiling information. The returned data is
468 * binary: the sampling step and the actual contents of the profile
469 * buffer. Use of the program readprofile is recommended in order to
470 * get meaningful info out of these data.
473 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
475 unsigned long p = *ppos;
478 unsigned int sample_step = 1 << prof_shift;
480 profile_flip_buffers();
481 if (p >= (prof_len+1)*sizeof(unsigned int))
483 if (count > (prof_len+1)*sizeof(unsigned int) - p)
484 count = (prof_len+1)*sizeof(unsigned int) - p;
487 while (p < sizeof(unsigned int) && count > 0) {
488 if (put_user(*((char *)(&sample_step)+p), buf))
490 buf++; p++; count--; read++;
492 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
493 if (copy_to_user(buf, (void *)pnt, count))
501 * Writing to /proc/profile resets the counters
503 * Writing a 'profiling multiplier' value into it also re-sets the profiling
504 * interrupt frequency, on architectures that support this.
506 static ssize_t write_profile(struct file *file, const char __user *buf,
507 size_t count, loff_t *ppos)
510 extern int setup_profiling_timer(unsigned int multiplier);
512 if (count == sizeof(int)) {
513 unsigned int multiplier;
515 if (copy_from_user(&multiplier, buf, sizeof(int)))
518 if (setup_profiling_timer(multiplier))
522 profile_discard_flip_buffers();
523 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
527 static const struct file_operations proc_profile_operations = {
528 .read = read_profile,
529 .write = write_profile,
530 .llseek = default_llseek,
534 static void profile_nop(void *unused)
538 static int create_hash_tables(void)
542 for_each_online_cpu(cpu) {
543 int node = cpu_to_mem(cpu);
546 page = __alloc_pages_node(node,
547 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
551 per_cpu(cpu_profile_hits, cpu)[1]
552 = (struct profile_hit *)page_address(page);
553 page = __alloc_pages_node(node,
554 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
558 per_cpu(cpu_profile_hits, cpu)[0]
559 = (struct profile_hit *)page_address(page);
565 on_each_cpu(profile_nop, NULL, 1);
566 for_each_online_cpu(cpu) {
569 if (per_cpu(cpu_profile_hits, cpu)[0]) {
570 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
571 per_cpu(cpu_profile_hits, cpu)[0] = NULL;
574 if (per_cpu(cpu_profile_hits, cpu)[1]) {
575 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
576 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
583 #define create_hash_tables() ({ 0; })
586 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
588 struct proc_dir_entry *entry;
594 cpu_notifier_register_begin();
596 if (create_hash_tables()) {
601 entry = proc_create("profile", S_IWUSR | S_IRUGO,
602 NULL, &proc_profile_operations);
605 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
606 __hotcpu_notifier(profile_cpu_callback, 0);
609 cpu_notifier_register_done();
612 subsys_initcall(create_proc_profile);
613 #endif /* CONFIG_PROC_FS */