linux-kernel - Re: [PATCH v2 2/2] x86: add prefetching to do

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Message-ID: <20131106185936.GA11415@hmsreliant.think-freely.org>
Date:	Wed, 6 Nov 2013 13:59:36 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Dave Jones <davej@...hat.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
Subject: Re: [PATCH v2 2/2] x86: add prefetching to do_csum

On Wed, Nov 06, 2013 at 10:23:10AM -0800, Eric Dumazet wrote:
> On Wed, 2013-11-06 at 10:54 -0500, Neil Horman wrote:
> 
> > My guess was that the whole comment was made in reference to the fact that
> > checksum offload negated all these advantages.  Thats not so true anymore, since
> > infiniband needs csum in software for ipoib.
> > 
> > I'll fix this up and send a v3, but I'll give it a day in case there are more
> > comments first.
> 
> Also please include netdev, I think people there are interested.
> 
Sure, will do in the updated version

> I caught this message, but I usually cannot read lkml traffic.
> 
> I wonder why you do not use (and/or change/tune) prefetch_range()
> instead of a local definition.
> 
I wanted to look into this further, because I wasn't (yet) sure if it was  a bug
or not, but from what I can see x86_64 doesn't define ARCH_HAS_PREFECTH.  That
makes prefetch_range() a nop (I confirmed this via objdump).  It seems like we
should either define ARCH_HAS_PREFETCH on x86_64, or we should remove the
#ifdef from prefetch_range
> 
> 
> 
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