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![Ken Chen](/assets/img/avatar_default.png)
schedstat is useful in investigating CPU scheduler behavior. Ideally, I think it is beneficial to have it on all the time. However, the cost of turning it on in production system is quite high, largely due to number of events it collects and also due to its large memory footprint. Most of the fields probably don't need to be full 64-bit on 64-bit arch. Rolling over 4 billion events will most like take a long time and user space tool can be made to accommodate that. I'm proposing kernel to cut back most of variable width on 64-bit system. (note, the following patch doesn't affect 32-bit system). Signed-off-by: Ken Chen <kenchen@google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
235 lines
7 KiB
C
235 lines
7 KiB
C
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#ifdef CONFIG_SCHEDSTATS
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/*
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* bump this up when changing the output format or the meaning of an existing
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* format, so that tools can adapt (or abort)
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*/
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#define SCHEDSTAT_VERSION 14
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static int show_schedstat(struct seq_file *seq, void *v)
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{
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int cpu;
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seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
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seq_printf(seq, "timestamp %lu\n", jiffies);
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for_each_online_cpu(cpu) {
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struct rq *rq = cpu_rq(cpu);
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#ifdef CONFIG_SMP
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struct sched_domain *sd;
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int dcount = 0;
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#endif
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/* runqueue-specific stats */
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seq_printf(seq,
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"cpu%d %u %u %u %u %u %u %u %u %u %llu %llu %lu",
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cpu, rq->yld_both_empty,
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rq->yld_act_empty, rq->yld_exp_empty, rq->yld_count,
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rq->sched_switch, rq->sched_count, rq->sched_goidle,
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rq->ttwu_count, rq->ttwu_local,
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rq->rq_sched_info.cpu_time,
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rq->rq_sched_info.run_delay, rq->rq_sched_info.pcount);
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seq_printf(seq, "\n");
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#ifdef CONFIG_SMP
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/* domain-specific stats */
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preempt_disable();
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for_each_domain(cpu, sd) {
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enum cpu_idle_type itype;
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char mask_str[NR_CPUS];
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cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
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seq_printf(seq, "domain%d %s", dcount++, mask_str);
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for (itype = CPU_IDLE; itype < CPU_MAX_IDLE_TYPES;
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itype++) {
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seq_printf(seq, " %u %u %u %u %u %u %u %u",
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sd->lb_count[itype],
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sd->lb_balanced[itype],
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sd->lb_failed[itype],
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sd->lb_imbalance[itype],
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sd->lb_gained[itype],
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sd->lb_hot_gained[itype],
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sd->lb_nobusyq[itype],
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sd->lb_nobusyg[itype]);
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}
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seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u %u\n",
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sd->alb_count, sd->alb_failed, sd->alb_pushed,
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sd->sbe_count, sd->sbe_balanced, sd->sbe_pushed,
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sd->sbf_count, sd->sbf_balanced, sd->sbf_pushed,
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sd->ttwu_wake_remote, sd->ttwu_move_affine,
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sd->ttwu_move_balance);
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}
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preempt_enable();
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#endif
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}
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return 0;
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}
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static int schedstat_open(struct inode *inode, struct file *file)
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{
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unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
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char *buf = kmalloc(size, GFP_KERNEL);
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struct seq_file *m;
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int res;
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if (!buf)
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return -ENOMEM;
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res = single_open(file, show_schedstat, NULL);
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if (!res) {
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m = file->private_data;
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m->buf = buf;
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m->size = size;
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} else
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kfree(buf);
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return res;
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}
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const struct file_operations proc_schedstat_operations = {
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.open = schedstat_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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/*
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* Expects runqueue lock to be held for atomicity of update
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*/
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static inline void
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rq_sched_info_arrive(struct rq *rq, unsigned long long delta)
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{
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if (rq) {
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rq->rq_sched_info.run_delay += delta;
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rq->rq_sched_info.pcount++;
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}
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}
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/*
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* Expects runqueue lock to be held for atomicity of update
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*/
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static inline void
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rq_sched_info_depart(struct rq *rq, unsigned long long delta)
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{
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if (rq)
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rq->rq_sched_info.cpu_time += delta;
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}
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# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
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# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
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# define schedstat_set(var, val) do { var = (val); } while (0)
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#else /* !CONFIG_SCHEDSTATS */
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static inline void
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rq_sched_info_arrive(struct rq *rq, unsigned long long delta)
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{}
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static inline void
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rq_sched_info_depart(struct rq *rq, unsigned long long delta)
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{}
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# define schedstat_inc(rq, field) do { } while (0)
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# define schedstat_add(rq, field, amt) do { } while (0)
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# define schedstat_set(var, val) do { } while (0)
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#endif
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#ifdef CONFIG_SCHEDSTATS
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/*
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* Called when a process is dequeued from the active array and given
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* the cpu. We should note that with the exception of interactive
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* tasks, the expired queue will become the active queue after the active
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* queue is empty, without explicitly dequeuing and requeuing tasks in the
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* expired queue. (Interactive tasks may be requeued directly to the
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* active queue, thus delaying tasks in the expired queue from running;
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* see scheduler_tick()).
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*
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* This function is only called from sched_info_arrive(), rather than
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* dequeue_task(). Even though a task may be queued and dequeued multiple
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* times as it is shuffled about, we're really interested in knowing how
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* long it was from the *first* time it was queued to the time that it
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* finally hit a cpu.
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*/
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static inline void sched_info_dequeued(struct task_struct *t)
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{
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t->sched_info.last_queued = 0;
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}
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/*
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* Called when a task finally hits the cpu. We can now calculate how
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* long it was waiting to run. We also note when it began so that we
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* can keep stats on how long its timeslice is.
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*/
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static void sched_info_arrive(struct task_struct *t)
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{
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unsigned long long now = sched_clock(), delta = 0;
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if (t->sched_info.last_queued)
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delta = now - t->sched_info.last_queued;
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sched_info_dequeued(t);
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t->sched_info.run_delay += delta;
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t->sched_info.last_arrival = now;
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t->sched_info.pcount++;
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rq_sched_info_arrive(task_rq(t), delta);
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}
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/*
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* Called when a process is queued into either the active or expired
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* array. The time is noted and later used to determine how long we
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* had to wait for us to reach the cpu. Since the expired queue will
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* become the active queue after active queue is empty, without dequeuing
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* and requeuing any tasks, we are interested in queuing to either. It
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* is unusual but not impossible for tasks to be dequeued and immediately
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* requeued in the same or another array: this can happen in sched_yield(),
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* set_user_nice(), and even load_balance() as it moves tasks from runqueue
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* to runqueue.
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*
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* This function is only called from enqueue_task(), but also only updates
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* the timestamp if it is already not set. It's assumed that
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* sched_info_dequeued() will clear that stamp when appropriate.
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*/
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static inline void sched_info_queued(struct task_struct *t)
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{
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if (unlikely(sched_info_on()))
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if (!t->sched_info.last_queued)
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t->sched_info.last_queued = sched_clock();
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}
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/*
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* Called when a process ceases being the active-running process, either
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* voluntarily or involuntarily. Now we can calculate how long we ran.
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*/
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static inline void sched_info_depart(struct task_struct *t)
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{
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unsigned long long delta = sched_clock() - t->sched_info.last_arrival;
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t->sched_info.cpu_time += delta;
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rq_sched_info_depart(task_rq(t), delta);
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}
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/*
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* Called when tasks are switched involuntarily due, typically, to expiring
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* their time slice. (This may also be called when switching to or from
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* the idle task.) We are only called when prev != next.
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*/
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static inline void
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__sched_info_switch(struct task_struct *prev, struct task_struct *next)
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{
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struct rq *rq = task_rq(prev);
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/*
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* prev now departs the cpu. It's not interesting to record
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* stats about how efficient we were at scheduling the idle
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* process, however.
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*/
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if (prev != rq->idle)
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sched_info_depart(prev);
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if (next != rq->idle)
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sched_info_arrive(next);
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}
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static inline void
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sched_info_switch(struct task_struct *prev, struct task_struct *next)
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{
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if (unlikely(sched_info_on()))
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__sched_info_switch(prev, next);
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}
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#else
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#define sched_info_queued(t) do { } while (0)
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#define sched_info_switch(t, next) do { } while (0)
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#endif /* CONFIG_SCHEDSTATS */
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