kernel/delayacct.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* delayacct.c - per-task delay accounting
   3  *
   4  * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   5  */
   6
   7 #include <linux/sched.h>
   8 #include <linux/sched/task.h>
   9 #include <linux/sched/cputime.h>
  10 #include <linux/sched/clock.h>
  11 #include <linux/slab.h>
  12 #include <linux/taskstats.h>
  13 #include <linux/sysctl.h>
  14 #include <linux/delayacct.h>
  15 #include <linux/module.h>
  16
  17 DEFINE_STATIC_KEY_FALSE(delayacct_key);
  18 int delayacct_on __read_mostly; /* Delay accounting turned on/off */
  19 struct kmem_cache *delayacct_cache;
  20
  21 static void set_delayacct(bool enabled)
  22 {
  23         if (enabled) {
  24                 static_branch_enable(&delayacct_key);
  25                 delayacct_on = 1;
  26         } else {
  27                 delayacct_on = 0;
  28                 static_branch_disable(&delayacct_key);
  29         }
  30 }
  31
  32 static int __init delayacct_setup_enable(char *str)
  33 {
  34         delayacct_on = 1;
  35         return 1;
  36 }
  37 __setup("delayacct", delayacct_setup_enable);
  38
  39 void delayacct_init(void)
  40 {
  41         delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
  42         delayacct_tsk_init(&init_task);
  43         set_delayacct(delayacct_on);
  44 }
  45
  46 #ifdef CONFIG_PROC_SYSCTL
  47 int sysctl_delayacct(struct ctl_table *table, int write, void *buffer,
  48                      size_t *lenp, loff_t *ppos)
  49 {
  50         int state = delayacct_on;
  51         struct ctl_table t;
  52         int err;
  53
  54         if (write && !capable(CAP_SYS_ADMIN))
  55                 return -EPERM;
  56
  57         t = *table;
  58         t.data = &state;
  59         err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
  60         if (err < 0)
  61                 return err;
  62         if (write)
  63                 set_delayacct(state);
  64         return err;
  65 }
  66 #endif
  67
  68 void __delayacct_tsk_init(struct task_struct *tsk)
  69 {
  70         tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
  71         if (tsk->delays)
  72                 raw_spin_lock_init(&tsk->delays->lock);
  73 }
  74
  75 /*
  76  * Finish delay accounting for a statistic using its timestamps (@start),
  77  * accumalator (@total) and @count
  78  */
  79 static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total, u32 *count)
  80 {
  81         s64 ns = local_clock() - *start;
  82         unsigned long flags;
  83
  84         if (ns > 0) {
  85                 raw_spin_lock_irqsave(lock, flags);
  86                 *total += ns;
  87                 (*count)++;
  88                 raw_spin_unlock_irqrestore(lock, flags);
  89         }
  90 }
  91
  92 void __delayacct_blkio_start(void)
  93 {
  94         current->delays->blkio_start = local_clock();
  95 }
  96
  97 /*
  98  * We cannot rely on the `current` macro, as we haven't yet switched back to
  99  * the process being woken.
 100  */
 101 void __delayacct_blkio_end(struct task_struct *p)
 102 {
 103         struct task_delay_info *delays = p->delays;
 104         u64 *total;
 105         u32 *count;
 106
 107         if (p->delays->flags & DELAYACCT_PF_SWAPIN) {
 108                 total = &delays->swapin_delay;
 109                 count = &delays->swapin_count;
 110         } else {
 111                 total = &delays->blkio_delay;
 112                 count = &delays->blkio_count;
 113         }
 114
 115         delayacct_end(&delays->lock, &delays->blkio_start, total, count);
 116 }
 117
 118 int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 119 {
 120         u64 utime, stime, stimescaled, utimescaled;
 121         unsigned long long t2, t3;
 122         unsigned long flags, t1;
 123         s64 tmp;
 124
 125         task_cputime(tsk, &utime, &stime);
 126         tmp = (s64)d->cpu_run_real_total;
 127         tmp += utime + stime;
 128         d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
 129
 130         task_cputime_scaled(tsk, &utimescaled, &stimescaled);
 131         tmp = (s64)d->cpu_scaled_run_real_total;
 132         tmp += utimescaled + stimescaled;
 133         d->cpu_scaled_run_real_total =
 134                 (tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
 135
 136         /*
 137          * No locking available for sched_info (and too expensive to add one)
 138          * Mitigate by taking snapshot of values
 139          */
 140         t1 = tsk->sched_info.pcount;
 141         t2 = tsk->sched_info.run_delay;
 142         t3 = tsk->se.sum_exec_runtime;
 143
 144         d->cpu_count += t1;
 145
 146         tmp = (s64)d->cpu_delay_total + t2;
 147         d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
 148
 149         tmp = (s64)d->cpu_run_virtual_total + t3;
 150         d->cpu_run_virtual_total =
 151                 (tmp < (s64)d->cpu_run_virtual_total) ? 0 : tmp;
 152
 153         if (!tsk->delays)
 154                 return 0;
 155
 156         /* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
 157
 158         raw_spin_lock_irqsave(&tsk->delays->lock, flags);
 159         tmp = d->blkio_delay_total + tsk->delays->blkio_delay;
 160         d->blkio_delay_total = (tmp < d->blkio_delay_total) ? 0 : tmp;
 161         tmp = d->swapin_delay_total + tsk->delays->swapin_delay;
 162         d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 163         tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 164         d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
 165         tmp = d->thrashing_delay_total + tsk->delays->thrashing_delay;
 166         d->thrashing_delay_total = (tmp < d->thrashing_delay_total) ? 0 : tmp;
 167         d->blkio_count += tsk->delays->blkio_count;
 168         d->swapin_count += tsk->delays->swapin_count;
 169         d->freepages_count += tsk->delays->freepages_count;
 170         d->thrashing_count += tsk->delays->thrashing_count;
 171         raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 172
 173         return 0;
 174 }
 175
 176 __u64 __delayacct_blkio_ticks(struct task_struct *tsk)
 177 {
 178         __u64 ret;
 179         unsigned long flags;
 180
 181         raw_spin_lock_irqsave(&tsk->delays->lock, flags);
 182         ret = nsec_to_clock_t(tsk->delays->blkio_delay +
 183                                 tsk->delays->swapin_delay);
 184         raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 185         return ret;
 186 }
 187
 188 void __delayacct_freepages_start(void)
 189 {
 190         current->delays->freepages_start = local_clock();
 191 }
 192
 193 void __delayacct_freepages_end(void)
 194 {
 195         delayacct_end(&current->delays->lock,
 196                       &current->delays->freepages_start,
 197                       &current->delays->freepages_delay,
 198                       &current->delays->freepages_count);
 199 }
 200
 201 void __delayacct_thrashing_start(void)
 202 {
 203         current->delays->thrashing_start = local_clock();
 204 }
 205
 206 void __delayacct_thrashing_end(void)
 207 {
 208         delayacct_end(&current->delays->lock,
 209                       &current->delays->thrashing_start,
 210                       &current->delays->thrashing_delay,
 211                       &current->delays->thrashing_count);
 212 }