On Fri, May 02, 2014 at 11:26:24PM +0200, Thomas Gleixner wrote:
> Russell reported, that irqtime_account_idle_ticks() takes ages due to:
>
> for (i = 0; i < ticks; i++)
> irqtime_account_process_tick(current, 0, rq);
>
> It's sad, that this code was written way _AFTER_ the NOHZ idle
> functionality was available. I charge myself guitly for not paying
> attention when that crap got merged with commit abb74cefa (sched:
> Export ns irqtimes through /proc/stat)
>
> So instead of looping nr_ticks times just apply the whole thing at
> once.
>
> As a side note: The whole cputime_t vs. u64 business in that context
> wants to be cleaned up as well. There is no point in having all these
> back and forth conversions. Lets standardise on u64 nsec for all
> kernel internal accounting and be done with it. Everything else does
> not make sense at all for fine grained accounting. Frederic, can you
> please take care of that?
>
> Reported-by: Russell King <rmk+ker...@arm.linux.org.uk>
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
> Cc: sta...@vger.kernel.org
One nit below, other than that:
Reviewed-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> ---
> kernel/sched/cputime.c | 32 ++++++++++++++++----------------
> 1 file changed, 16 insertions(+), 16 deletions(-)
>
> Index: linux-2.6/kernel/sched/cputime.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched/cputime.c
> +++ linux-2.6/kernel/sched/cputime.c
> @@ -332,50 +332,50 @@ out:
> * 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)
> + struct rq *rq, int ticks)
> {
> - cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
> + cputime_t scaled = cputime_to_scaled(cputime_one_jiffy);
> + u64 cputime = (__force u64) cputime_one_jiffy;
> u64 *cpustat = kcpustat_this_cpu->cpustat;
>
> if (steal_account_process_tick())
> return;
>
> + cputime *= ticks;
> + scaled *= ticks;
> +
> if (irqtime_account_hi_update()) {
> - cpustat[CPUTIME_IRQ] += (__force u64) cputime_one_jiffy;
> + cpustat[CPUTIME_IRQ] += cputime;
> } else if (irqtime_account_si_update()) {
> - cpustat[CPUTIME_SOFTIRQ] += (__force u64) cputime_one_jiffy;
> + cpustat[CPUTIME_SOFTIRQ] += cputime;
> } else if (this_cpu_ksoftirqd() == p) {
> /*
> * ksoftirqd time do not get accounted in cpu_softirq_time.
> * So, we have to handle it separately here.
> * Also, p->stime needs to be updated for ksoftirqd.
> */
> - __account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
> - CPUTIME_SOFTIRQ);
> + __account_system_time(p, cputime, scaled, CPUTIME_SOFTIRQ);
> } else if (user_tick) {
> - account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
> + account_user_time(p, cputime, scaled);
> } else if (p == rq->idle) {
> - account_idle_time(cputime_one_jiffy);
> + account_idle_time(cputime);
> } else if (p->flags & PF_VCPU) { /* System time or guest time */
> - account_guest_time(p, cputime_one_jiffy, one_jiffy_scaled);
> + account_guest_time(p, cputime, scaled);
> } else {
> - __account_system_time(p, cputime_one_jiffy, one_jiffy_scaled,
> - CPUTIME_SYSTEM);
> + __account_system_time(p, cputime, scaled, CPUTIME_SYSTEM);
Stray tab character.
> }
> }
>
> 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);
> + irqtime_account_process_tick(current, 0, rq, ticks);
> }
> #else /* CONFIG_IRQ_TIME_ACCOUNTING */
> static inline void irqtime_account_idle_ticks(int ticks) {}
> static inline void irqtime_account_process_tick(struct task_struct *p, int
> user_tick,
> - struct rq *rq) {}
> + struct rq *rq, int nr_ticks) {}
> #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
>
> /*
> @@ -464,7 +464,7 @@ void account_process_tick(struct task_st
> return;
>
> if (sched_clock_irqtime) {
> - irqtime_account_process_tick(p, user_tick, rq);
> + irqtime_account_process_tick(p, user_tick, rq, 1);
> return;
> }
>
>
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