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

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Date:	Tue, 15 Oct 2013 17:34:10 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Neil Horman <nhorman@...driver.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] x86: Run checksumming in parallel accross multiple alu's

On Tue, 2013-10-15 at 09:21 -0700, Joe Perches wrote:

> Ingo, Eric _showed_ that the prefetch is good here.
> How about looking at a little optimization to the minimal
> prefetch that gives that level of performance.

Wait a minute, my point was to remind that main cost is the
memory fetching.

Its nice to optimize cpu cycles if we are short of them,
but in the csum_partial() case, the bottleneck is the memory.

Also I was wondering on the implications of changing reads order,
as it might fool cpu predictions.

I do not particularly care about finding the right prefetch stride,
I think Intel guys know better than me.

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