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

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Message-ID: <1382035687.2045.155.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Thu, 17 Oct 2013 11:48:07 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"H. Peter Anvin" <hpa@...or.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>, x86@...nel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] x86: Run checksumming in parallel accross multiple alu's

On Thu, 2013-10-17 at 11:19 -0700, H. Peter Anvin wrote:

> Seriously, though, how much does it matter?  All the above seems likely
> to do is to drown the signal by adding noise.

I don't think so.

> 
> If the parallel (threaded) checksumming is faster, which theory says it
> should and microbenchmarking confirms, how important are the
> macrobenchmarks?

Seriously, micro benchmarks are very misleading.

I spent time on this patch, and found no changes on real workloads.

I was excited first, then disappointed.

I hope we will find the real issue, as I really don't care of micro
benchmarks.


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