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 UPDATE_DELAY(type) \
 18do { \
 19	d->type##_delay_max = tsk->delays->type##_delay_max; \
 20	d->type##_delay_min = tsk->delays->type##_delay_min; \
 21	tmp = d->type##_delay_total + tsk->delays->type##_delay; \
 22	d->type##_delay_total = (tmp < d->type##_delay_total) ? 0 : tmp; \
 23	d->type##_count += tsk->delays->type##_count; \
 24} while (0)
 25
 26DEFINE_STATIC_KEY_FALSE(delayacct_key);
 27int delayacct_on __read_mostly;	/* Delay accounting turned on/off */
 28struct kmem_cache *delayacct_cache;
 29
 30static void set_delayacct(bool enabled)
 31{
 32	if (enabled) {
 33		static_branch_enable(&delayacct_key);
 34		delayacct_on = 1;
 35	} else {
 36		delayacct_on = 0;
 37		static_branch_disable(&delayacct_key);
 38	}
 39}
 40
 41static int __init delayacct_setup_enable(char *str)
 42{
 43	delayacct_on = 1;
 44	return 1;
 45}
 46__setup("delayacct", delayacct_setup_enable);
 47
 48void delayacct_init(void)
 49{
 50	delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
 51	delayacct_tsk_init(&init_task);
 52	set_delayacct(delayacct_on);
 53}
 54
 55#ifdef CONFIG_PROC_SYSCTL
 56static int sysctl_delayacct(const struct ctl_table *table, int write, void *buffer,
 57		     size_t *lenp, loff_t *ppos)
 58{
 59	int state = delayacct_on;
 60	struct ctl_table t;
 61	int err;
 62
 63	if (write && !capable(CAP_SYS_ADMIN))
 64		return -EPERM;
 65
 66	t = *table;
 67	t.data = &state;
 68	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
 69	if (err < 0)
 70		return err;
 71	if (write)
 72		set_delayacct(state);
 73	return err;
 74}
 75
 76static const struct ctl_table kern_delayacct_table[] = {
 77	{
 78		.procname       = "task_delayacct",
 79		.data           = NULL,
 80		.maxlen         = sizeof(unsigned int),
 81		.mode           = 0644,
 82		.proc_handler   = sysctl_delayacct,
 83		.extra1         = SYSCTL_ZERO,
 84		.extra2         = SYSCTL_ONE,
 85	},
 86};
 87
 88static __init int kernel_delayacct_sysctls_init(void)
 89{
 90	register_sysctl_init("kernel", kern_delayacct_table);
 91	return 0;
 92}
 93late_initcall(kernel_delayacct_sysctls_init);
 94#endif
 95
 96void __delayacct_tsk_init(struct task_struct *tsk)
 97{
 98	tsk->delays = kmem_cache_zalloc(delayacct_cache, GFP_KERNEL);
 99	if (tsk->delays)
100		raw_spin_lock_init(&tsk->delays->lock);
101}
102
103/*
104 * Finish delay accounting for a statistic using its timestamps (@start),
105 * accumulator (@total) and @count
106 */
107static void delayacct_end(raw_spinlock_t *lock, u64 *start, u64 *total, u32 *count, u64 *max, u64 *min)
108{
109	s64 ns = local_clock() - *start;
110	unsigned long flags;
111
112	if (ns > 0) {
113		raw_spin_lock_irqsave(lock, flags);
114		*total += ns;
115		(*count)++;
116		if (ns > *max)
117			*max = ns;
118		if (*min == 0 || ns < *min)
119			*min = ns;
120		raw_spin_unlock_irqrestore(lock, flags);
121	}
122}
123
124void __delayacct_blkio_start(void)
125{
126	current->delays->blkio_start = local_clock();
127}
128
129/*
130 * We cannot rely on the `current` macro, as we haven't yet switched back to
131 * the process being woken.
132 */
133void __delayacct_blkio_end(struct task_struct *p)
134{
135	delayacct_end(&p->delays->lock,
136		      &p->delays->blkio_start,
137		      &p->delays->blkio_delay,
138		      &p->delays->blkio_count,
139		      &p->delays->blkio_delay_max,
140		      &p->delays->blkio_delay_min);
141}
142
143int delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
144{
145	u64 utime, stime, stimescaled, utimescaled;
146	unsigned long long t2, t3;
147	unsigned long flags, t1;
148	s64 tmp;
149
150	task_cputime(tsk, &utime, &stime);
151	tmp = (s64)d->cpu_run_real_total;
152	tmp += utime + stime;
153	d->cpu_run_real_total = (tmp < (s64)d->cpu_run_real_total) ? 0 : tmp;
154
155	task_cputime_scaled(tsk, &utimescaled, &stimescaled);
156	tmp = (s64)d->cpu_scaled_run_real_total;
157	tmp += utimescaled + stimescaled;
158	d->cpu_scaled_run_real_total =
159		(tmp < (s64)d->cpu_scaled_run_real_total) ? 0 : tmp;
160
161	/*
162	 * No locking available for sched_info (and too expensive to add one)
163	 * Mitigate by taking snapshot of values
164	 */
165	t1 = tsk->sched_info.pcount;
166	t2 = tsk->sched_info.run_delay;
167	t3 = tsk->se.sum_exec_runtime;
168
169	d->cpu_count += t1;
170
171	d->cpu_delay_max = tsk->sched_info.max_run_delay;
172	d->cpu_delay_min = tsk->sched_info.min_run_delay;
173	tmp = (s64)d->cpu_delay_total + t2;
174	d->cpu_delay_total = (tmp < (s64)d->cpu_delay_total) ? 0 : tmp;
175	tmp = (s64)d->cpu_run_virtual_total + t3;
176
177	d->cpu_run_virtual_total =
178		(tmp < (s64)d->cpu_run_virtual_total) ?	0 : tmp;
179
180	if (!tsk->delays)
181		return 0;
182
183	/* zero XXX_total, non-zero XXX_count implies XXX stat overflowed */
184	raw_spin_lock_irqsave(&tsk->delays->lock, flags);
185	UPDATE_DELAY(blkio);
186	UPDATE_DELAY(swapin);
187	UPDATE_DELAY(freepages);
188	UPDATE_DELAY(thrashing);
189	UPDATE_DELAY(compact);
190	UPDATE_DELAY(wpcopy);
191	UPDATE_DELAY(irq);
192	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
193
194	return 0;
195}
196
197__u64 __delayacct_blkio_ticks(struct task_struct *tsk)
198{
199	__u64 ret;
200	unsigned long flags;
201
202	raw_spin_lock_irqsave(&tsk->delays->lock, flags);
203	ret = nsec_to_clock_t(tsk->delays->blkio_delay);
204	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
205	return ret;
206}
207
208void __delayacct_freepages_start(void)
209{
210	current->delays->freepages_start = local_clock();
211}
212
213void __delayacct_freepages_end(void)
214{
215	delayacct_end(&current->delays->lock,
216		      &current->delays->freepages_start,
217		      &current->delays->freepages_delay,
218		      &current->delays->freepages_count,
219		      &current->delays->freepages_delay_max,
220		      &current->delays->freepages_delay_min);
221}
222
223void __delayacct_thrashing_start(bool *in_thrashing)
224{
225	*in_thrashing = !!current->in_thrashing;
226	if (*in_thrashing)
227		return;
228
229	current->in_thrashing = 1;
230	current->delays->thrashing_start = local_clock();
231}
232
233void __delayacct_thrashing_end(bool *in_thrashing)
234{
235	if (*in_thrashing)
236		return;
237
238	current->in_thrashing = 0;
239	delayacct_end(&current->delays->lock,
240		      &current->delays->thrashing_start,
241		      &current->delays->thrashing_delay,
242		      &current->delays->thrashing_count,
243		      &current->delays->thrashing_delay_max,
244		      &current->delays->thrashing_delay_min);
245}
246
247void __delayacct_swapin_start(void)
248{
249	current->delays->swapin_start = local_clock();
250}
251
252void __delayacct_swapin_end(void)
253{
254	delayacct_end(&current->delays->lock,
255		      &current->delays->swapin_start,
256		      &current->delays->swapin_delay,
257		      &current->delays->swapin_count,
258		      &current->delays->swapin_delay_max,
259		      &current->delays->swapin_delay_min);
260}
261
262void __delayacct_compact_start(void)
263{
264	current->delays->compact_start = local_clock();
265}
266
267void __delayacct_compact_end(void)
268{
269	delayacct_end(&current->delays->lock,
270		      &current->delays->compact_start,
271		      &current->delays->compact_delay,
272		      &current->delays->compact_count,
273		      &current->delays->compact_delay_max,
274		      &current->delays->compact_delay_min);
275}
276
277void __delayacct_wpcopy_start(void)
278{
279	current->delays->wpcopy_start = local_clock();
280}
281
282void __delayacct_wpcopy_end(void)
283{
284	delayacct_end(&current->delays->lock,
285		      &current->delays->wpcopy_start,
286		      &current->delays->wpcopy_delay,
287		      &current->delays->wpcopy_count,
288		      &current->delays->wpcopy_delay_max,
289		      &current->delays->wpcopy_delay_min);
290}
291
292void __delayacct_irq(struct task_struct *task, u32 delta)
293{
294	unsigned long flags;
295
296	raw_spin_lock_irqsave(&task->delays->lock, flags);
297	task->delays->irq_delay += delta;
298	task->delays->irq_count++;
299	if (delta > task->delays->irq_delay_max)
300		task->delays->irq_delay_max = delta;
301	if (delta && (!task->delays->irq_delay_min || delta < task->delays->irq_delay_min))
302		task->delays->irq_delay_min = delta;
303	raw_spin_unlock_irqrestore(&task->delays->lock, flags);
304}
305