From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>,
Suresh Siddha <suresh.b.siddha@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue()
Date: Wed, 10 Oct 2012 15:05:55 +0200 [thread overview]
Message-ID: <1349874355.1279.16.camel@twins> (raw)
In-Reply-To: <20121010122921.GX29125@suse.de>
On Wed, 2012-10-10 at 13:29 +0100, Mel Gorman wrote:
> Do we really switch more though?
>
> Look at the difference in interrupts vs context switch. IPIs are an interrupt
> so if TTWU_QUEUE wakes process B using an IPI, does that count as a context
> switch?
Nope. Nor would it for NO_TTWU_QUEUE. A process waking another is just
that, a wakeup.
A context switch is when we stop running a process and start running
anther. A wakeup can lead to us deciding the newly woken task is a
better task to run, however its not a given.
next prev parent reply other threads:[~2012-10-10 13:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-02 6:51 Netperf UDP_STREAM regression due to not sending IPIs in ttwu_queue() Mel Gorman
2012-10-02 7:49 ` Mike Galbraith
2012-10-02 8:45 ` Mel Gorman
2012-10-02 9:31 ` Mike Galbraith
2012-10-02 13:14 ` Mel Gorman
2012-10-02 14:33 ` Mike Galbraith
2012-10-03 6:50 ` Mike Galbraith
2012-10-03 8:13 ` Mike Galbraith
2012-10-03 13:30 ` Mike Galbraith
2012-10-10 12:29 ` Mel Gorman
2012-10-10 13:02 ` Mike Galbraith
2012-10-10 13:05 ` Peter Zijlstra [this message]
2012-10-02 22:48 ` Rick Jones
2012-10-03 9:47 ` Mel Gorman
2012-10-03 10:22 ` Eric Dumazet
2012-10-03 18:04 ` Rick Jones
2012-10-05 9:54 ` Mel Gorman
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