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

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Message-ID: <1382116835.3284.23.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Fri, 18 Oct 2013 10:20:35 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Ingo Molnar <mingo@...nel.org>, 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 Fri, 2013-10-18 at 12:50 -0400, Neil Horman wrote:
> > 

> 	for(i=0;i<100000;i++) {
> 		sum = csum_partial(buf+offset, PAGE_SIZE, sum);
> 		offset = (offset < BUFSIZ-PAGE_SIZE) ? offset+PAGE_SIZE  : 0;
> 	}

Please replace this by random accesses, and use the more standard 1500
length.

offset = prandom_u32() % (BUFSIZ - 1500);
offset &= ~1U;

sum = csum_partial(buf + offset, 1500, sum);

You are basically doing sequential accesses, so prefetch should
be automatically done by cpu itself.

Thanks !


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