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   1 /* delayacct.c - per-task delay accounting
   2  *
   3  * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   4  *
   5  * This program is free software;  you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it would be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
  13  * the GNU General Public License for more details.
  14  */
  15
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18 #include <linux/time.h>
  19 #include <linux/sysctl.h>
  20 #include <linux/delayacct.h>
  21
  22 int delayacct_on __read_mostly; /* Delay accounting turned on/off */
  23 kmem_cache_t *delayacct_cache;
  24
  25 static int __init delayacct_setup_enable(char *str)
  26 {
  27         delayacct_on = 1;
  28         return 1;
  29 }
  30 __setup("delayacct", delayacct_setup_enable);
  31
  32 void delayacct_init(void)
  33 {
  34         delayacct_cache = kmem_cache_create("delayacct_cache",
  35                                         sizeof(struct task_delay_info),
  36                                         0,
  37                                         SLAB_PANIC,
  38                                         NULL, NULL);
  39         delayacct_tsk_init(&init_task);
  40 }
  41
  42 void __delayacct_tsk_init(struct task_struct *tsk)
  43 {
  44         tsk->delays = kmem_cache_zalloc(delayacct_cache, SLAB_KERNEL);
  45         if (tsk->delays)
  46                 spin_lock_init(&tsk->delays->lock);
  47 }
  48
  49 void __delayacct_tsk_exit(struct task_struct *tsk)
  50 {
  51         kmem_cache_free(delayacct_cache, tsk->delays);
  52         tsk->delays = NULL;
  53 }
  54
  55 /*
  56  * Start accounting for a delay statistic using
  57  * its starting timestamp (@start)
  58  */
  59
  60 static inline void delayacct_start(struct timespec *start)
  61 {
  62         do_posix_clock_monotonic_gettime(start);
  63 }
  64
  65 /*
  66  * Finish delay accounting for a statistic using
  67  * its timestamps (@start, @end), accumalator (@total) and @count
  68  */
  69
  70 static void delayacct_end(struct timespec *start, struct timespec *end,
  71                                 u64 *total, u32 *count)
  72 {
  73         struct timespec ts;
  74         s64 ns;
  75
  76         do_posix_clock_monotonic_gettime(end);
  77         ts = timespec_sub(*end, *start);
  78         ns = timespec_to_ns(&ts);
  79         if (ns < 0)
  80                 return;
  81
  82         spin_lock(&current->delays->lock);
  83         *total += ns;
  84         (*count)++;
  85         spin_unlock(&current->delays->lock);
  86 }
  87