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SubjectRe: [PATCH 6/6] Account ksoftirqd time as cpustat softirq -v1
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On Mon, 2010-10-25 at 15:30 -0700, Venkatesh Pallipadi wrote:
> softirq time in ksoftirqd context is not accounted in ns granularity
> per cpu softirq stats, as we want that to be a part of ksoftirqd
> exec_runtime.
>
> Accounting them as softirq on /proc/stat separately.
>
> Tested-by: Shaun Ruffell <sruffell@digium.com>
>
> Signed-off-by: Venkatesh Pallipadi <venki@google.com>
> ---
> kernel/sched.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 49f6f61..0955050 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -3617,6 +3617,14 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
> cpustat->irq = cputime64_add(cpustat->irq, tmp);
> } else if (irqtime_account_si_update()) {
> cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
> + } 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,
> + &cpustat->softirq);
> } else if (user_tick) {
> account_user_time(p, cputime_one_jiffy, one_jiffy_scaled);
> } else if (p == rq->idle) {


I'm somewhat confused by this patch.. This is significantly different
from the thing proposed last time around, which was to use:

cpustat->softirq + this_cpu_ksoftirqd()->se.sum_exec_runtime

The above looses the fine grained aspect of the accounting and simply
charges a whole jiffy if the current process happens to be ksoftirqd.




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