linux-kernel - Re: [PATCH 5/5] Account ksoftirqd time as cpustat softirq -v2

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Message-ID: <1293009621.2170.72.camel@laptop>
Date:	Wed, 22 Dec 2010 10:20:21 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Shaun Ruffell <sruffell@...ium.com>
Subject: Re: [PATCH 5/5] Account ksoftirqd time as cpustat softirq -v2

On Tue, 2010-12-21 at 17:09 -0800, 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@...ium.com>
> Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
> ---
>  kernel/sched.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 193b1d0..4ff6d1a 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -3819,6 +3819,14 @@ 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) {

So you add the ksoftirqd runtime as softirq time in the /proc/stat
output?

That seems dubious...
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