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From: Paul Menage <paul@paulmenage.org>
Date: Sat, 20 Aug 2011 00:45:48 -0700
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Subject: Re: [RFC PATCH 00/32] Nohz cpusets (was: Nohz Tasks)
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
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        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Paul Menage <menage@google.com>,
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On Thu, Aug 18, 2011 at 6:25 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote:
>>
>> Why not do it unconditionally?  That is, if all the conditions are
>> fulfilled, disable the tick regardless of any cpuset settings.
>
> Because I'm not sure it's a win on every workload. This involves
> some hooks here and there (syscall slow path), IPIs, etc...

I agree with Avi. I'd be inclined to investigate further to see if
there are any important workloads on which it's not a win - and then
add the extra complexity to control it from cpusets if necessary.
Unless there's really a good reason to make it configurable, it's
simpler to make it unconditional.

Paul