linux-kernel - Re: [patch] Remove the per cpu tick skew

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Message-ID: <AANLkTim3h4VNqF97d++k4_4g-4hnw57YXJSQgSEP4S7m@mail.gmail.com>
Date:	Wed, 28 Jul 2010 16:50:40 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	linux-arch@...r.kernel.org
Subject: Re: [patch] Remove the per cpu tick skew

On Wed, Jul 28, 2010 at 1:26 PM, john stultz <johnstul@...ibm.com> wrote:
> On Tue, Jul 27, 2010 at 9:02 PM, Arjan van de Ven <arjan@...radead.org> wrote:
>> Historically, Linux has tried to make the regular timer tick on the various
>> CPUs not happen at the same time, to avoid contention on xtime_lock.
>>
>> Nowadays, with the tickless kernel, this contention no longer happens
>> since time keeping and updating are done differently. In addition,
>> this skew is actually hurting power consumption in a measurable
>> way on many-core systems.
>>
>
> I'll give it a spin against -rt and see if we show any latency jumps.

In my testing on a 8way box, I didn't see any concerning latencies
with this patch running cyclictest or a FIFO99 gtod loop.

thanks
-john
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