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1 | /* |
2 | * kernel/time/timer_stats.c |
3 | * |
4 | * Collect timer usage statistics. |
5 | * |
6 | * Copyright(C) 2006, Red Hat, Inc., Ingo Molnar |
7 | * Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> |
8 | * |
9 | * timer_stats is based on timer_top, a similar functionality which was part of |
10 | * Con Kolivas dyntick patch set. It was developed by Daniel Petrini at the |
11 | * Instituto Nokia de Tecnologia - INdT - Manaus. timer_top's design was based |
12 | * on dynamic allocation of the statistics entries and linear search based |
13 | * lookup combined with a global lock, rather than the static array, hash |
14 | * and per-CPU locking which is used by timer_stats. It was written for the |
15 | * pre hrtimer kernel code and therefore did not take hrtimers into account. |
16 | * Nevertheless it provided the base for the timer_stats implementation and |
17 | * was a helpful source of inspiration. Kudos to Daniel and the Nokia folks |
18 | * for this effort. |
19 | * |
20 | * timer_top.c is |
21 | * Copyright (C) 2005 Instituto Nokia de Tecnologia - INdT - Manaus |
22 | * Written by Daniel Petrini <d.pensator@gmail.com> |
23 | * timer_top.c was released under the GNU General Public License version 2 |
24 | * |
25 | * We export the addresses and counting of timer functions being called, |
26 | * the pid and cmdline from the owner process if applicable. |
27 | * |
28 | * Start/stop data collection: |
29 | * # echo [1|0] >/proc/timer_stats |
30 | * |
31 | * Display the information collected so far: |
32 | * # cat /proc/timer_stats |
33 | * |
34 | * This program is free software; you can redistribute it and/or modify |
35 | * it under the terms of the GNU General Public License version 2 as |
36 | * published by the Free Software Foundation. |
37 | */ |
38 | |
39 | #include <linux/proc_fs.h> |
40 | #include <linux/module.h> |
41 | #include <linux/spinlock.h> |
42 | #include <linux/sched.h> |
43 | #include <linux/seq_file.h> |
44 | #include <linux/kallsyms.h> |
45 | |
46 | #include <asm/uaccess.h> |
47 | |
48 | /* |
49 | * This is our basic unit of interest: a timer expiry event identified |
50 | * by the timer, its start/expire functions and the PID of the task that |
51 | * started the timer. We count the number of times an event happens: |
52 | */ |
53 | struct entry { |
54 | /* |
55 | * Hash list: |
56 | */ |
57 | struct entry *next; |
58 | |
59 | /* |
60 | * Hash keys: |
61 | */ |
62 | void *timer; |
63 | void *start_func; |
64 | void *expire_func; |
65 | pid_t pid; |
66 | |
67 | /* |
68 | * Number of timeout events: |
69 | */ |
70 | unsigned long count; |
71 | unsigned int timer_flag; |
72 | |
73 | /* |
74 | * We save the command-line string to preserve |
75 | * this information past task exit: |
76 | */ |
77 | char comm[TASK_COMM_LEN + 1]; |
78 | |
79 | } ____cacheline_aligned_in_smp; |
80 | |
81 | /* |
82 | * Spinlock protecting the tables - not taken during lookup: |
83 | */ |
84 | static DEFINE_SPINLOCK(table_lock); |
85 | |
86 | /* |
87 | * Per-CPU lookup locks for fast hash lookup: |
88 | */ |
89 | static DEFINE_PER_CPU(raw_spinlock_t, tstats_lookup_lock); |
90 | |
91 | /* |
92 | * Mutex to serialize state changes with show-stats activities: |
93 | */ |
94 | static DEFINE_MUTEX(show_mutex); |
95 | |
96 | /* |
97 | * Collection status, active/inactive: |
98 | */ |
99 | int __read_mostly timer_stats_active; |
100 | |
101 | /* |
102 | * Beginning/end timestamps of measurement: |
103 | */ |
104 | static ktime_t time_start, time_stop; |
105 | |
106 | /* |
107 | * tstat entry structs only get allocated while collection is |
108 | * active and never freed during that time - this simplifies |
109 | * things quite a bit. |
110 | * |
111 | * They get freed when a new collection period is started. |
112 | */ |
113 | #define MAX_ENTRIES_BITS 10 |
114 | #define MAX_ENTRIES (1UL << MAX_ENTRIES_BITS) |
115 | |
116 | static unsigned long nr_entries; |
117 | static struct entry entries[MAX_ENTRIES]; |
118 | |
119 | static atomic_t overflow_count; |
120 | |
121 | /* |
122 | * The entries are in a hash-table, for fast lookup: |
123 | */ |
124 | #define TSTAT_HASH_BITS (MAX_ENTRIES_BITS - 1) |
125 | #define TSTAT_HASH_SIZE (1UL << TSTAT_HASH_BITS) |
126 | #define TSTAT_HASH_MASK (TSTAT_HASH_SIZE - 1) |
127 | |
128 | #define __tstat_hashfn(entry) \ |
129 | (((unsigned long)(entry)->timer ^ \ |
130 | (unsigned long)(entry)->start_func ^ \ |
131 | (unsigned long)(entry)->expire_func ^ \ |
132 | (unsigned long)(entry)->pid ) & TSTAT_HASH_MASK) |
133 | |
134 | #define tstat_hashentry(entry) (tstat_hash_table + __tstat_hashfn(entry)) |
135 | |
136 | static struct entry *tstat_hash_table[TSTAT_HASH_SIZE] __read_mostly; |
137 | |
138 | static void reset_entries(void) |
139 | { |
140 | nr_entries = 0; |
141 | memset(entries, 0, sizeof(entries)); |
142 | memset(tstat_hash_table, 0, sizeof(tstat_hash_table)); |
143 | atomic_set(&overflow_count, 0); |
144 | } |
145 | |
146 | static struct entry *alloc_entry(void) |
147 | { |
148 | if (nr_entries >= MAX_ENTRIES) |
149 | return NULL; |
150 | |
151 | return entries + nr_entries++; |
152 | } |
153 | |
154 | static int match_entries(struct entry *entry1, struct entry *entry2) |
155 | { |
156 | return entry1->timer == entry2->timer && |
157 | entry1->start_func == entry2->start_func && |
158 | entry1->expire_func == entry2->expire_func && |
159 | entry1->pid == entry2->pid; |
160 | } |
161 | |
162 | /* |
163 | * Look up whether an entry matching this item is present |
164 | * in the hash already. Must be called with irqs off and the |
165 | * lookup lock held: |
166 | */ |
167 | static struct entry *tstat_lookup(struct entry *entry, char *comm) |
168 | { |
169 | struct entry **head, *curr, *prev; |
170 | |
171 | head = tstat_hashentry(entry); |
172 | curr = *head; |
173 | |
174 | /* |
175 | * The fastpath is when the entry is already hashed, |
176 | * we do this with the lookup lock held, but with the |
177 | * table lock not held: |
178 | */ |
179 | while (curr) { |
180 | if (match_entries(curr, entry)) |
181 | return curr; |
182 | |
183 | curr = curr->next; |
184 | } |
185 | /* |
186 | * Slowpath: allocate, set up and link a new hash entry: |
187 | */ |
188 | prev = NULL; |
189 | curr = *head; |
190 | |
191 | spin_lock(&table_lock); |
192 | /* |
193 | * Make sure we have not raced with another CPU: |
194 | */ |
195 | while (curr) { |
196 | if (match_entries(curr, entry)) |
197 | goto out_unlock; |
198 | |
199 | prev = curr; |
200 | curr = curr->next; |
201 | } |
202 | |
203 | curr = alloc_entry(); |
204 | if (curr) { |
205 | *curr = *entry; |
206 | curr->count = 0; |
207 | curr->next = NULL; |
208 | memcpy(curr->comm, comm, TASK_COMM_LEN); |
209 | |
210 | smp_mb(); /* Ensure that curr is initialized before insert */ |
211 | |
212 | if (prev) |
213 | prev->next = curr; |
214 | else |
215 | *head = curr; |
216 | } |
217 | out_unlock: |
218 | spin_unlock(&table_lock); |
219 | |
220 | return curr; |
221 | } |
222 | |
223 | /** |
224 | * timer_stats_update_stats - Update the statistics for a timer. |
225 | * @timer: pointer to either a timer_list or a hrtimer |
226 | * @pid: the pid of the task which set up the timer |
227 | * @startf: pointer to the function which did the timer setup |
228 | * @timerf: pointer to the timer callback function of the timer |
229 | * @comm: name of the process which set up the timer |
230 | * |
231 | * When the timer is already registered, then the event counter is |
232 | * incremented. Otherwise the timer is registered in a free slot. |
233 | */ |
234 | void timer_stats_update_stats(void *timer, pid_t pid, void *startf, |
235 | void *timerf, char *comm, |
236 | unsigned int timer_flag) |
237 | { |
238 | /* |
239 | * It doesn't matter which lock we take: |
240 | */ |
241 | raw_spinlock_t *lock; |
242 | struct entry *entry, input; |
243 | unsigned long flags; |
244 | |
245 | if (likely(!timer_stats_active)) |
246 | return; |
247 | |
248 | lock = &per_cpu(tstats_lookup_lock, raw_smp_processor_id()); |
249 | |
250 | input.timer = timer; |
251 | input.start_func = startf; |
252 | input.expire_func = timerf; |
253 | input.pid = pid; |
254 | input.timer_flag = timer_flag; |
255 | |
256 | raw_spin_lock_irqsave(lock, flags); |
257 | if (!timer_stats_active) |
258 | goto out_unlock; |
259 | |
260 | entry = tstat_lookup(&input, comm); |
261 | if (likely(entry)) |
262 | entry->count++; |
263 | else |
264 | atomic_inc(&overflow_count); |
265 | |
266 | out_unlock: |
267 | raw_spin_unlock_irqrestore(lock, flags); |
268 | } |
269 | |
270 | static void print_name_offset(struct seq_file *m, unsigned long addr) |
271 | { |
272 | char symname[KSYM_NAME_LEN]; |
273 | |
274 | if (lookup_symbol_name(addr, symname) < 0) |
275 | seq_printf(m, "<%p>", (void *)addr); |
276 | else |
277 | seq_printf(m, "%s", symname); |
278 | } |
279 | |
280 | static int tstats_show(struct seq_file *m, void *v) |
281 | { |
282 | struct timespec period; |
283 | struct entry *entry; |
284 | unsigned long ms; |
285 | long events = 0; |
286 | ktime_t time; |
287 | int i; |
288 | |
289 | mutex_lock(&show_mutex); |
290 | /* |
291 | * If still active then calculate up to now: |
292 | */ |
293 | if (timer_stats_active) |
294 | time_stop = ktime_get(); |
295 | |
296 | time = ktime_sub(time_stop, time_start); |
297 | |
298 | period = ktime_to_timespec(time); |
299 | ms = period.tv_nsec / 1000000; |
300 | |
301 | seq_puts(m, "Timer Stats Version: v0.2\n"); |
302 | seq_printf(m, "Sample period: %ld.%03ld s\n", period.tv_sec, ms); |
303 | if (atomic_read(&overflow_count)) |
304 | seq_printf(m, "Overflow: %d entries\n", |
305 | atomic_read(&overflow_count)); |
306 | |
307 | for (i = 0; i < nr_entries; i++) { |
308 | entry = entries + i; |
309 | if (entry->timer_flag & TIMER_STATS_FLAG_DEFERRABLE) { |
310 | seq_printf(m, "%4luD, %5d %-16s ", |
311 | entry->count, entry->pid, entry->comm); |
312 | } else { |
313 | seq_printf(m, " %4lu, %5d %-16s ", |
314 | entry->count, entry->pid, entry->comm); |
315 | } |
316 | |
317 | print_name_offset(m, (unsigned long)entry->start_func); |
318 | seq_puts(m, " ("); |
319 | print_name_offset(m, (unsigned long)entry->expire_func); |
320 | seq_puts(m, ")\n"); |
321 | |
322 | events += entry->count; |
323 | } |
324 | |
325 | ms += period.tv_sec * 1000; |
326 | if (!ms) |
327 | ms = 1; |
328 | |
329 | if (events && period.tv_sec) |
330 | seq_printf(m, "%ld total events, %ld.%03ld events/sec\n", |
331 | events, events * 1000 / ms, |
332 | (events * 1000000 / ms) % 1000); |
333 | else |
334 | seq_printf(m, "%ld total events\n", events); |
335 | |
336 | mutex_unlock(&show_mutex); |
337 | |
338 | return 0; |
339 | } |
340 | |
341 | /* |
342 | * After a state change, make sure all concurrent lookup/update |
343 | * activities have stopped: |
344 | */ |
345 | static void sync_access(void) |
346 | { |
347 | unsigned long flags; |
348 | int cpu; |
349 | |
350 | for_each_online_cpu(cpu) { |
351 | raw_spinlock_t *lock = &per_cpu(tstats_lookup_lock, cpu); |
352 | |
353 | raw_spin_lock_irqsave(lock, flags); |
354 | /* nothing */ |
355 | raw_spin_unlock_irqrestore(lock, flags); |
356 | } |
357 | } |
358 | |
359 | static ssize_t tstats_write(struct file *file, const char __user *buf, |
360 | size_t count, loff_t *offs) |
361 | { |
362 | char ctl[2]; |
363 | |
364 | if (count != 2 || *offs) |
365 | return -EINVAL; |
366 | |
367 | if (copy_from_user(ctl, buf, count)) |
368 | return -EFAULT; |
369 | |
370 | mutex_lock(&show_mutex); |
371 | switch (ctl[0]) { |
372 | case '0': |
373 | if (timer_stats_active) { |
374 | timer_stats_active = 0; |
375 | time_stop = ktime_get(); |
376 | sync_access(); |
377 | } |
378 | break; |
379 | case '1': |
380 | if (!timer_stats_active) { |
381 | reset_entries(); |
382 | time_start = ktime_get(); |
383 | smp_mb(); |
384 | timer_stats_active = 1; |
385 | } |
386 | break; |
387 | default: |
388 | count = -EINVAL; |
389 | } |
390 | mutex_unlock(&show_mutex); |
391 | |
392 | return count; |
393 | } |
394 | |
395 | static int tstats_open(struct inode *inode, struct file *filp) |
396 | { |
397 | return single_open(filp, tstats_show, NULL); |
398 | } |
399 | |
400 | static const struct file_operations tstats_fops = { |
401 | .open = tstats_open, |
402 | .read = seq_read, |
403 | .write = tstats_write, |
404 | .llseek = seq_lseek, |
405 | .release = single_release, |
406 | }; |
407 | |
408 | void __init init_timer_stats(void) |
409 | { |
410 | int cpu; |
411 | |
412 | for_each_possible_cpu(cpu) |
413 | raw_spin_lock_init(&per_cpu(tstats_lookup_lock, cpu)); |
414 | } |
415 | |
416 | static int __init init_tstats_procfs(void) |
417 | { |
418 | struct proc_dir_entry *pe; |
419 | |
420 | pe = proc_create("timer_stats", 0644, NULL, &tstats_fops); |
421 | if (!pe) |
422 | return -ENOMEM; |
423 | return 0; |
424 | } |
425 | __initcall(init_tstats_procfs); |
426 |
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