From: Robert Love <rml@tech9.net>
To: Mike Kravetz <kravetz@us.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: set_cpus_allowed() optimization
Date: 13 May 2002 16:05:46 -0700 [thread overview]
Message-ID: <1021331147.18799.2997.camel@summit> (raw)
In-Reply-To: <20020510130903.B1544@w-mikek2.des.beaverton.ibm.com>
n Fri, 2002-05-10 at 13:09, Mike Kravetz wrote:
> Please consider the following optimization to set_cpus_allowed().
> In the case where the task does not reside on a runqueue, is it
> not safe/sufficient to simply set the task's cpu field? This
> would avoid scheduling the migration thread to perform the task.
>
> Previously, set_cpus_allowed() was always called for a task that
> resides on a runqueue. With the introduction of the 'cpu affinity'
> system calls, this is no longer the case.
I like! I agree, if the task is not runnable then it should be
sufficient to just set task->cpu as when it is activated it will be put
into the runqueue based on ->cpu.
There was a chance even without the CPU affinity runqueues a process
would dequeue before set_cpus_allowed returned. Look at the case in
migration_thread where exactly what your patch does is done. If !array,
then the code just sets task->cpu and returns.
Ingo? Good?
Robert Love
prev parent reply other threads:[~2002-05-13 23:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-10 20:09 set_cpus_allowed() optimization Mike Kravetz
2002-05-13 23:05 ` Robert Love [this message]
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