linux-kernel - Re: preemption and rwsems (was: Re: missing madvise functionality)

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Message-ID: <20070406194010.GA21322@elte.hu>
Date:	Fri, 6 Apr 2007 21:40:10 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Howells <dhowells@...hat.com>,
	Jakub Jelinek <jakub@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Rik van Riel <riel@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Hugh Dickins <hugh@...itas.com>
Subject: Re: preemption and rwsems (was: Re: missing madvise functionality)


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> > i've attached an updated version of trace-it.c, which will turn this 
> > off itself, using a sysctl. I also made WAKEUP_TIMING default-off.
> 
> ok.  http://userweb.kernel.org/~akpm/to-ingo.txt is the trace of
> 
> 	taskset -c 0 ./jakubs-test-app
> 
> while the system was doing the 150,000 context switches/sec.
> 
> It isn't very interesting.

this shows an idle CPU#7: you should taskset -c 0 trace-it too - it only 
traces the current CPU by default. (there's the 
/proc/sys/kernel/trace_all_cpus flag to trace all cpus, but in this case 
we really want the trace of CPU#0)

	Ingo
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