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

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Message-ID: <20131101195850.GD8467@hmsreliant.think-freely.org>
Date:	Fri, 1 Nov 2013 15:58:50 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Joe Perches <joe@...ches.com>
Cc:	David Laight <David.Laight@...LAB.COM>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Doug Ledford <dledford@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

On Fri, Nov 01, 2013 at 12:45:29PM -0700, Joe Perches wrote:
> On Fri, 2013-11-01 at 13:37 -0400, Neil Horman wrote:
> 
> > I think it would be better if we just did the prefetch here
> > and re-addressed this area when AVX (or addcx/addox) instructions were available
> > for testing on hardware.
> 
> Could there be a difference if only a single software
> prefetch was done at the beginning of transfer before
> the while loop and hardware prefetches did the rest?
> 

I wouldn't think so.  If hardware was going to do any prefetching based on
memory access patterns it will do so regardless of the leading prefetch, and
that first prefetch isn't helpful because we still wind up stalling on the adds
while its completing
Neil

> 
> 
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