netdev - Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

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Date:	Tue, 29 Oct 2013 09:07:12 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org, sebastien.dugue@...l.net,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

On Tue, Oct 29, 2013 at 01:52:33PM +0100, Ingo Molnar wrote:
> 
> * Neil Horman <nhorman@...driver.com> wrote:
> 
> > On Tue, Oct 29, 2013 at 12:30:31PM +0100, Ingo Molnar wrote:
> > > 
> > > * Neil Horman <nhorman@...driver.com> wrote:
> > > 
> > > > Sure it was this:
> > > > for i in `seq 0 1 3`
> > > > do
> > > > echo $i > /sys/module/csum_test/parameters/module_test_mode
> > > > taskset -c 0 perf stat --repeat 20 -C 0 -ddd perf bench sched messaging -- /root/test.sh
> > > > done >> counters.txt 2>&1
> > > > 
> > > > where test.sh is:
> > > > #!/bin/sh
> > > > echo 1 > /sys/module/csum_test/parameters/test_fire
> > > 
> > > What does '-- /root/test.sh' do?
> > > 
> > > Unless I'm missing something, the line above will run:
> > > 
> > >   perf bench sched messaging -- /root/test.sh
> > > 
> > > which should be equivalent to:
> > > 
> > >   perf bench sched messaging
> > > 
> > > i.e. /root/test.sh won't be run.
> > 
> > According to the perf man page, I'm supposed to be able to use -- 
> > to separate perf command line parameters from the command I want 
> > to run.  And it definately executed test.sh, I added an echo to 
> > stdout in there as a test run and observed them get captured in 
> > counters.txt
> 
> Well, '--' can be used to delineate the command portion for cases 
> where it's ambiguous.
> 
> Here's it's unambiguous though. This:
> 
>   perf stat --repeat 20 -C 0 -ddd perf bench sched messaging -- /root/test.sh
> 
> stops parsing a valid option after the -ddd option, so in theory it 
> should execute 'perf bench sched messaging -- /root/test.sh' where 
> '-- /root/test.sh' is simply a parameter to 'perf bench' and is thus 
> ignored.
> 
> The message output you provided seems to suggest that to be the 
> case:
> 
>  Performance counter stats for 'perf bench sched messaging -- bash -c echo 1 > /sys/module/csum_test/parameters/test_fire' (20 runs):
> 
> See how the command executed by perf stat was 'perf bench ...'.
> 
> Did you want to run:
> 
>   perf stat --repeat 20 -C 0 -ddd /root/test.sh
> 
I'm sure it worked properly on my system here, I specificially checked it, but
I'll gladly run it again.  You have to give me an hour as I have a meeting to
run to, but I'll have results shortly.
Neil

> ?
> 
> Thanks,
> 
> 	Ingo
> 
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