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sched: Export ns irqtimes through /proc/stat

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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: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292980144-28796-5-git-send-email-venki@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Venkatesh Pallipadi 2010-12-21 17:09:03 -08:00 • committed by Ingo Molnar
commit abb74cefa9
1 changed files with 102 additions and 0 deletions
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102
kernel/sched.c
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@ -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));
}