From: Peter Zijlstra <peterz@infradead.org>
To: minyard@acm.org
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Corey Minyard <cminyard@mvista.com>
Subject: Re: [PATCH] sched: Initialize rq->age_stamp on processor start
Date: Thu, 8 May 2014 18:13:37 +0200 [thread overview]
Message-ID: <20140508161337.GF30445@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1399405857-14056-1-git-send-email-minyard@acm.org>
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On Tue, May 06, 2014 at 02:50:57PM -0500, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> If the sched_clock time starts at a large value, the kernel will spin
> in sched_avg_update for a long time while rq->age_stamp catches up
> with rq->clock.
>
> The comment in kernel/sched/clock.c says that there is no strict promise
> that it starts at zero. So initialize rq->age_stamp when a cpu starts up
> to avoid this.
>
> I was seeing long delays on a simulator that didn't start the clock at
> zero. This might also be an issue on reboots on processors that don't
> re-initialize the timer to zero on reset, and when using kexec.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
This patch made my cris-defconfig build fail.
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next prev parent reply other threads:[~2014-05-08 16:13 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-06 19:50 [PATCH] sched: Initialize rq->age_stamp on processor start minyard
2014-05-08 16:13 ` Peter Zijlstra [this message]
2014-05-08 18:47 ` Corey Minyard
2014-05-08 18:47 ` minyard
2014-05-09 9:12 ` Peter Zijlstra
2014-05-19 13:10 ` [tip:sched/core] sched: Initialize rq-> age_stamp " tip-bot for Corey Minyard
2014-05-22 12:28 ` tip-bot for Corey Minyard
-- strict thread matches above, loose matches on Subject: below --
2014-03-18 0:05 [PATCH] sched: Initialize rq->age_stamp " minyard
2014-03-18 4:06 ` Mike Galbraith
2014-03-18 8:56 ` Peter Zijlstra
2014-03-18 9:25 ` Mike Galbraith
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