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Commit abb74cef authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Ingo Molnar
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sched: Export ns irqtimes through /proc/stat 



CONFIG_IRQ_TIME_ACCOUNTING adds ns granularity irq time on each CPU.
This info is already used in scheduler to do proper task chargeback
(earlier patches). This patch retro-fits this ns granularity
hardirq and softirq information to /proc/stat irq and softirq fields.

The update is still done on timer tick, where we look at accumulated
ns hardirq/softirq time and account the tick to user/system/irq/hardirq/guest
accordingly.

No new interface added.

Earlier versions looked at adding this as new fields in some /proc
files. This one seems to be the best in terms of impact to existing
apps, even though it has somewhat more kernel code than earlier versions.

Tested-by: default avatarShaun Ruffell <sruffell@digium.com>
Signed-off-by: default avatarVenkatesh Pallipadi <venki@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292980144-28796-5-git-send-email-venki@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 70a89a66

kernel/sched.c

+102 −0
Original line number Diff line number Diff line
@@ -1920,8 +1920,40 @@ static void update_rq_clock_task(struct rq *rq, s64 delta) 
		sched_rt_avg_update(rq, irq_delta);

}



static int irqtime_account_hi_update(void)

{

	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;

	unsigned long flags;

	u64 latest_ns;

	int ret = 0;



	local_irq_save(flags);

	latest_ns = this_cpu_read(cpu_hardirq_time);

	if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->irq))

		ret = 1;

	local_irq_restore(flags);

	return ret;

}



static int irqtime_account_si_update(void)

{

	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;

	unsigned long flags;

	u64 latest_ns;

	int ret = 0;



	local_irq_save(flags);

	latest_ns = this_cpu_read(cpu_softirq_time);

	if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->softirq))

		ret = 1;

	local_irq_restore(flags);

	return ret;

}



#else /* CONFIG_IRQ_TIME_ACCOUNTING */



#define sched_clock_irqtime	(0)



static void update_rq_clock_task(struct rq *rq, s64 delta)

{

	rq->clock_task += delta;
@@ -3621,6 +3653,65 @@ void account_system_time(struct task_struct *p, int hardirq_offset, 
	__account_system_time(p, cputime, cputime_scaled, target_cputime64);

}



#ifdef CONFIG_IRQ_TIME_ACCOUNTING

/*

 * Account a tick to a process and cpustat

 * @p: the process that the cpu time gets accounted to

 * @user_tick: is the tick from userspace

 * @rq: the pointer to rq

 *

 * Tick demultiplexing follows the order

 * - pending hardirq update

 * - pending softirq update

 * - user_time

 * - idle_time

 * - system time

 *   - check for guest_time

 *   - else account as system_time

 *

 * Check for hardirq is done both for system and user time as there is

 * no timer going off while we are on hardirq and hence we may never get an

 * opportunity to update it solely in system time.

 * p->stime and friends are only updated on system time and not on irq

 * softirq as those do not count in task exec_runtime any more.

 */

static void irqtime_account_process_tick(struct task_struct *p, int user_tick,

						struct rq *rq)

{

	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);

	cputime64_t tmp = cputime_to_cputime64(cputime_one_jiffy);

	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;



	if (irqtime_account_hi_update()) {

		cpustat->irq = cputime64_add(cpustat->irq, tmp);

	} else if (irqtime_account_si_update()) {

		cpustat->softirq = cputime64_add(cpustat->softirq, tmp);

	} else if (user_tick) {

		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);

	} else if (p == rq->idle) {

		account_idle_time(cputime_one_jiffy);

	} else if (p->flags & PF_VCPU) { /* System time or guest time */

		account_guest_time(p, cputime_one_jiffy, one_jiffy_scaled);

	} else {

		__account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,

					&cpustat->system);

	}

}



static void irqtime_account_idle_ticks(int ticks)

{

	int i;

	struct rq *rq = this_rq();



	for (i = 0; i < ticks; i++)

		irqtime_account_process_tick(current, 0, rq);

}

#else

static void irqtime_account_idle_ticks(int ticks) {}

static void irqtime_account_process_tick(struct task_struct *p, int user_tick,

						struct rq *rq) {}

#endif



/*

 * Account for involuntary wait time.

 * @steal: the cpu time spent in involuntary wait
@@ -3661,6 +3752,11 @@ void account_process_tick(struct task_struct *p, int user_tick) 
	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);

	struct rq *rq = this_rq();



	if (sched_clock_irqtime) {

		irqtime_account_process_tick(p, user_tick, rq);

		return;

	}



	if (user_tick)

		account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);

	else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
@@ -3686,6 +3782,12 @@ void account_steal_ticks(unsigned long ticks) 
 */

void account_idle_ticks(unsigned long ticks)

{



	if (sched_clock_irqtime) {

		irqtime_account_idle_ticks(ticks);

		return;

	}



	account_idle_time(jiffies_to_cputime(ticks));

}