linux-kernel - Re: [PATCH net-next] hyperv: Add support for Virtual Receive Side Scaling (vRSS)

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Message-ID: <1387490744.1876.52.camel@bwh-desktop.uk.level5networks.com>
Date:	Thu, 19 Dec 2013 22:05:44 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Tom Herbert <therbert@...gle.com>
CC:	Haiyang Zhang <haiyangz@...rosoft.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>
Subject: Re: [PATCH net-next] hyperv: Add support for Virtual Receive Side
 Scaling (vRSS)

On Thu, 2013-12-19 at 13:43 -0800, Tom Herbert wrote:
> Patch is below. This version did most pre-computation of the variants
> I built, but results in largest table (40*256*4 bytes), This gives
> performance roughly comparable with jhash (roughly same as jhash for
> IPv4, about 30% more cycles for IPv6). I have the simpler less memory
> intensive versions also if you're interested, these are 10x worse
> cycles so I wouldn't want those in critical path.
> ----
> Introduce Toeplitz hash functions. Toeplitz is a hash used primarily in
> NICs to performan RSS flow steering.  This is a software implemenation
> of that. In order to make the hash calculation efficient, we precompute
> the possible hash values for each inidividual byte of input. The input
> length is up to 40 bytes, so we make an array of cache[40][256].
[...]

You haven't addressed my comments here:
<http://article.gmane.org/gmane.linux.network/284753>

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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