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From: Peter Zijlstra <peterz@infradead.org>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>, Will Deacon <will@kernel.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Allen Pais <allen.lkml@gmail.com>,
	Romain Perier <romain.perier@gmail.com>
Subject: Re: [PATCH] sched/cputime: correct account of irqtime
Date: Wed, 14 Oct 2020 15:02:23 +0200	[thread overview]
Message-ID: <20201014130223.GF2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1602510644-24536-1-git-send-email-kernelfans@gmail.com>

On Mon, Oct 12, 2020 at 09:50:44PM +0800, Pingfan Liu wrote:
> __do_softirq() may be interrupted by hardware interrupts. In this case,
> irqtime_account_irq() will account the time slice as CPUTIME_SOFTIRQ by
> mistake.
> 
> By passing irqtime_account_irq() an extra param about either hardirq or
> softirq, irqtime_account_irq() can handle the above case.

I'm not sure I see the scenario in which it goes wrong.

irqtime_account_irq() is designed such that we're called with the old
preempt_count on enter and the new preempt_count on exit. This way we'll
accumuate the delta to the previous context.

> @@ -68,7 +68,7 @@ void irqtime_account_irq(struct task_struct *curr)
>  	 */
>  	if (hardirq_count())
>  		irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
> -	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
> +	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd() && !hardirq)
>  		irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
>  }



  parent reply	other threads:[~2020-10-14 13:02 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 13:50 [PATCH] sched/cputime: correct account of irqtime Pingfan Liu
2020-10-13  3:10 ` jun qian
2020-10-13  4:22   ` Pingfan Liu
2020-10-14 13:02 ` Peter Zijlstra [this message]
2020-10-15  1:27   ` Pingfan Liu

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