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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
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, prof_shift;
42
43 int prof_on __read_mostly;
44 EXPORT_SYMBOL_GPL(prof_on);
45
46 static cpumask_var_t prof_cpu_mask;
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 int profile_setup(char *str)
54 {
55         static const char schedstr[] = "schedule";
56         static const char sleepstr[] = "sleep";
57         static const 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                 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
68                         prof_shift);
69 #else
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))
77                         prof_shift = par;
78                 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
79                         prof_shift);
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))
85                         prof_shift = par;
86                 pr_info("kernel KVM profiling enabled (shift: %ld)\n",
87                         prof_shift);
88         } else if (get_option(&str, &par)) {
89                 prof_shift = par;
90                 prof_on = CPU_PROFILING;
91                 pr_info("kernel profiling enabled (shift: %ld)\n",
92                         prof_shift);
93         }
94         return 1;
95 }
96 __setup("profile=", profile_setup);
97
98
99 int __ref profile_init(void)
100 {
101         int buffer_bytes;
102         if (!prof_on)
103                 return 0;
104
105         /* only text is profiled */
106         prof_len = (_etext - _stext) >> prof_shift;
107         buffer_bytes = prof_len*sizeof(atomic_t);
108
109         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
110                 return -ENOMEM;
111
112         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
113
114         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
115         if (prof_buffer)
116                 return 0;
117
118         prof_buffer = alloc_pages_exact(buffer_bytes,
119                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
120         if (prof_buffer)
121                 return 0;
122
123         prof_buffer = vzalloc(buffer_bytes);
124         if (prof_buffer)
125                 return 0;
126
127         free_cpumask_var(prof_cpu_mask);
128         return -ENOMEM;
129 }
130
131 /* Profile event notifications */
132
133 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
134 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
135 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
136
137 void profile_task_exit(struct task_struct *task)
138 {
139         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
140 }
141
142 int profile_handoff_task(struct task_struct *task)
143 {
144         int ret;
145         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
146         return (ret == NOTIFY_OK) ? 1 : 0;
147 }
148
149 void profile_munmap(unsigned long addr)
150 {
151         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
152 }
153
154 int task_handoff_register(struct notifier_block *n)
155 {
156         return atomic_notifier_chain_register(&task_free_notifier, n);
157 }
158 EXPORT_SYMBOL_GPL(task_handoff_register);
159
160 int task_handoff_unregister(struct notifier_block *n)
161 {
162         return atomic_notifier_chain_unregister(&task_free_notifier, n);
163 }
164 EXPORT_SYMBOL_GPL(task_handoff_unregister);
165
166 int profile_event_register(enum profile_type type, struct notifier_block *n)
167 {
168         int err = -EINVAL;
169
170         switch (type) {
171         case PROFILE_TASK_EXIT:
172                 err = blocking_notifier_chain_register(
173                                 &task_exit_notifier, n);
174                 break;
175         case PROFILE_MUNMAP:
176                 err = blocking_notifier_chain_register(
177                                 &munmap_notifier, n);
178                 break;
179         }
180
181         return err;
182 }
183 EXPORT_SYMBOL_GPL(profile_event_register);
184
185 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
186 {
187         int err = -EINVAL;
188
189         switch (type) {
190         case PROFILE_TASK_EXIT:
191                 err = blocking_notifier_chain_unregister(
192                                 &task_exit_notifier, n);
193                 break;
194         case PROFILE_MUNMAP:
195                 err = blocking_notifier_chain_unregister(
196                                 &munmap_notifier, n);
197                 break;
198         }
199
200         return err;
201 }
202 EXPORT_SYMBOL_GPL(profile_event_unregister);
203
204 #ifdef CONFIG_SMP
205 /*
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.
214  *
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
228  * process context).
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.
233  *
234  * -- nyc
235  */
236 static void __profile_flip_buffers(void *unused)
237 {
238         int cpu = smp_processor_id();
239
240         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
241 }
242
243 static void profile_flip_buffers(void)
244 {
245         int i, j, cpu;
246
247         mutex_lock(&profile_flip_mutex);
248         j = per_cpu(cpu_profile_flip, get_cpu());
249         put_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) {
254                         if (!hits[i].hits) {
255                                 if (hits[i].pc)
256                                         hits[i].pc = 0;
257                                 continue;
258                         }
259                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
260                         hits[i].hits = hits[i].pc = 0;
261                 }
262         }
263         mutex_unlock(&profile_flip_mutex);
264 }
265
266 static void profile_discard_flip_buffers(void)
267 {
268         int i, cpu;
269
270         mutex_lock(&profile_flip_mutex);
271         i = per_cpu(cpu_profile_flip, get_cpu());
272         put_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));
277         }
278         mutex_unlock(&profile_flip_mutex);
279 }
280
281 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
282 {
283         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
284         int i, j, cpu;
285         struct profile_hit *hits;
286
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;
290         cpu = get_cpu();
291         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
292         if (!hits) {
293                 put_cpu();
294                 return;
295         }
296         /*
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:
300          */
301         local_irq_save(flags);
302         do {
303                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
304                         if (hits[i + j].pc == pc) {
305                                 hits[i + j].hits += nr_hits;
306                                 goto out;
307                         } else if (!hits[i + j].hits) {
308                                 hits[i + j].pc = pc;
309                                 hits[i + j].hits = nr_hits;
310                                 goto out;
311                         }
312                 }
313                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
314         } while (i != primary);
315
316         /*
317          * Add the current hit(s) and flush the write-queue out
318          * to the global buffer:
319          */
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;
324         }
325 out:
326         local_irq_restore(flags);
327         put_cpu();
328 }
329
330 static int profile_cpu_callback(struct notifier_block *info,
331                                         unsigned long action, void *__cpu)
332 {
333         int node, cpu = (unsigned long)__cpu;
334         struct page *page;
335
336         switch (action) {
337         case CPU_UP_PREPARE:
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,
344                                         0);
345                         if (!page)
346                                 return notifier_from_errno(-ENOMEM);
347                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
348                 }
349                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
350                         page = __alloc_pages_node(node,
351                                         GFP_KERNEL | __GFP_ZERO,
352                                         0);
353                         if (!page)
354                                 goto out_free;
355                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
356                 }
357                 break;
358 out_free:
359                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
360                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
361                 __free_page(page);
362                 return notifier_from_errno(-ENOMEM);
363         case CPU_ONLINE:
364         case CPU_ONLINE_FROZEN:
365                 if (prof_cpu_mask != NULL)
366                         cpumask_set_cpu(cpu, prof_cpu_mask);
367                 break;
368         case CPU_UP_CANCELED:
369         case CPU_UP_CANCELED_FROZEN:
370         case CPU_DEAD:
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;
377                         __free_page(page);
378                 }
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;
382                         __free_page(page);
383                 }
384                 break;
385         }
386         return NOTIFY_OK;
387 }
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
392
393 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
394 {
395         unsigned long pc;
396         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
397         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
398 }
399 #endif /* !CONFIG_SMP */
400
401 void profile_hits(int type, void *__pc, unsigned int nr_hits)
402 {
403         if (prof_on != type || !prof_buffer)
404                 return;
405         do_profile_hits(type, __pc, nr_hits);
406 }
407 EXPORT_SYMBOL_GPL(profile_hits);
408
409 void profile_tick(int type)
410 {
411         struct pt_regs *regs = get_irq_regs();
412
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));
416 }
417
418 #ifdef CONFIG_PROC_FS
419 #include <linux/proc_fs.h>
420 #include <linux/seq_file.h>
421 #include <asm/uaccess.h>
422
423 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
424 {
425         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
426         return 0;
427 }
428
429 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
430 {
431         return single_open(file, prof_cpu_mask_proc_show, NULL);
432 }
433
434 static ssize_t prof_cpu_mask_proc_write(struct file *file,
435         const char __user *buffer, size_t count, loff_t *pos)
436 {
437         cpumask_var_t new_value;
438         int err;
439
440         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
441                 return -ENOMEM;
442
443         err = cpumask_parse_user(buffer, count, new_value);
444         if (!err) {
445                 cpumask_copy(prof_cpu_mask, new_value);
446                 err = count;
447         }
448         free_cpumask_var(new_value);
449         return err;
450 }
451
452 static const struct file_operations prof_cpu_mask_proc_fops = {
453         .open           = prof_cpu_mask_proc_open,
454         .read           = seq_read,
455         .llseek         = seq_lseek,
456         .release        = single_release,
457         .write          = prof_cpu_mask_proc_write,
458 };
459
460 void create_prof_cpu_mask(void)
461 {
462         /* create /proc/irq/prof_cpu_mask */
463         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
464 }
465
466 /*
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.
471  */
472 static ssize_t
473 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
474 {
475         unsigned long p = *ppos;
476         ssize_t read;
477         char *pnt;
478         unsigned int sample_step = 1 << prof_shift;
479
480         profile_flip_buffers();
481         if (p >= (prof_len+1)*sizeof(unsigned int))
482                 return 0;
483         if (count > (prof_len+1)*sizeof(unsigned int) - p)
484                 count = (prof_len+1)*sizeof(unsigned int) - p;
485         read = 0;
486
487         while (p < sizeof(unsigned int) && count > 0) {
488                 if (put_user(*((char *)(&sample_step)+p), buf))
489                         return -EFAULT;
490                 buf++; p++; count--; read++;
491         }
492         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
493         if (copy_to_user(buf, (void *)pnt, count))
494                 return -EFAULT;
495         read += count;
496         *ppos += read;
497         return read;
498 }
499
500 /*
501  * Writing to /proc/profile resets the counters
502  *
503  * Writing a 'profiling multiplier' value into it also re-sets the profiling
504  * interrupt frequency, on architectures that support this.
505  */
506 static ssize_t write_profile(struct file *file, const char __user *buf,
507                              size_t count, loff_t *ppos)
508 {
509 #ifdef CONFIG_SMP
510         extern int setup_profiling_timer(unsigned int multiplier);
511
512         if (count == sizeof(int)) {
513                 unsigned int multiplier;
514
515                 if (copy_from_user(&multiplier, buf, sizeof(int)))
516                         return -EFAULT;
517
518                 if (setup_profiling_timer(multiplier))
519                         return -EINVAL;
520         }
521 #endif
522         profile_discard_flip_buffers();
523         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
524         return count;
525 }
526
527 static const struct file_operations proc_profile_operations = {
528         .read           = read_profile,
529         .write          = write_profile,
530         .llseek         = default_llseek,
531 };
532
533 #ifdef CONFIG_SMP
534 static void profile_nop(void *unused)
535 {
536 }
537
538 static int create_hash_tables(void)
539 {
540         int cpu;
541
542         for_each_online_cpu(cpu) {
543                 int node = cpu_to_mem(cpu);
544                 struct page *page;
545
546                 page = __alloc_pages_node(node,
547                                 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
548                                 0);
549                 if (!page)
550                         goto out_cleanup;
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,
555                                 0);
556                 if (!page)
557                         goto out_cleanup;
558                 per_cpu(cpu_profile_hits, cpu)[0]
559                                 = (struct profile_hit *)page_address(page);
560         }
561         return 0;
562 out_cleanup:
563         prof_on = 0;
564         smp_mb();
565         on_each_cpu(profile_nop, NULL, 1);
566         for_each_online_cpu(cpu) {
567                 struct page *page;
568
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;
572                         __free_page(page);
573                 }
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;
577                         __free_page(page);
578                 }
579         }
580         return -1;
581 }
582 #else
583 #define create_hash_tables()                    ({ 0; })
584 #endif
585
586 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
587 {
588         struct proc_dir_entry *entry;
589         int err = 0;
590
591         if (!prof_on)
592                 return 0;
593
594         cpu_notifier_register_begin();
595
596         if (create_hash_tables()) {
597                 err = -ENOMEM;
598                 goto out;
599         }
600
601         entry = proc_create("profile", S_IWUSR | S_IRUGO,
602                             NULL, &proc_profile_operations);
603         if (!entry)
604                 goto out;
605         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
606         __hotcpu_notifier(profile_cpu_callback, 0);
607
608 out:
609         cpu_notifier_register_done();
610         return err;
611 }
612 subsys_initcall(create_proc_profile);
613 #endif /* CONFIG_PROC_FS */