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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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