From: Corey Minyard <cminyard@mvista.com>
To: Peter Zijlstra <peterz@infradead.org>, minyard@acm.org
Cc: Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: Initialize rq->age_stamp on processor start
Date: Thu, 08 May 2014 13:47:29 -0500 [thread overview]
Message-ID: <536BD141.7030000@mvista.com> (raw)
In-Reply-To: <20140508161337.GF30445@twins.programming.kicks-ass.net>
On 05/08/2014 11:13 AM, Peter Zijlstra wrote:
> 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.
Dang, I missed propagating a change. Yes, it's broken. One more time...
-corey
next prev parent reply other threads:[~2014-05-08 18:47 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
2014-05-08 18:47 ` Corey Minyard [this message]
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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