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SubjectRe: [PATCH] sched: account system time properly
Eric Dumazet wrote:

> On mostly idle cpu, irqs were thus not accounted and top or mpstat could tell
> user/admin that cpu was 100 % idle, 0.00 % irq, 0.00 % softirq, while it was not.
>
> Reported-by: Andrew Gallatin <gallatin@myri.com>
> Re-reported-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
> Tested-by: Eric Dumazet <dada1@cosmosbay.com>
> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index b902e58..26efa47 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4732,7 +4732,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
>
> if (user_tick)
> account_user_time(p, one_jiffy, one_jiffy_scaled);
> - else if (p != rq->idle)
> + else if ((p != rq->idle) || (irq_count() != HARDIRQ_OFFSET))
> account_system_time(p, HARDIRQ_OFFSET, one_jiffy,
> one_jiffy_scaled);
> else
>

I can confirm this fixes the issue for me. Thank you, and I am
sorry if my git-bisect fumble-fingers caused too much wasted time.

Cheers,

Drew


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