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

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Date:	Tue, 15 Oct 2013 16:15:28 +0200
From:	Sébastien Dugué <sebastien.dugue@...l.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	Neil Horman <nhorman@...driver.com>,
	<linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	<x86@...nel.org>
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple
 alu's

Hi Eric,

On Tue, 15 Oct 2013 07:06:25 -0700
Eric Dumazet <eric.dumazet@...il.com> wrote:

> On Tue, 2013-10-15 at 15:56 +0200, Sébastien Dugué wrote:
> > On Tue, 15 Oct 2013 15:33:36 +0200
> > Andi Kleen <andi@...stfloor.org> wrote:
> > 
> > > >   indeed, our typical workload is connected mode IPoIB on mlx4 QDR hardware
> > > > where one cannot benefit from hardware offloads.
> > > 
> > > Is this with sendfile?
> > 
> >   Tests were done with iperf at the time without any extra funky options, and
> > looking at the code it looks like it does plain write() / recv() on the socket.
> > 
> 
> But the csum cost is both for sender and receiver ?

  No, it was only on the receiver side that I noticed it.

> 
> Please post the following :
> 
> perf record -g "your iperf session"
> 
> perf report | head -n 200

  Sorry, but this is 3 years old stuff and I do not have the
setup anymore to reproduce.

  Sébastien.


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