netdev - Re: [PATCH v5] rfs: Receive Flow Steering

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Message-ID: <h2q412e6f7f1004171706w905cc5c8u51f82cad221642f4@mail.gmail.com>
Date:	Sun, 18 Apr 2010 08:06:44 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v5] rfs: Receive Flow Steering

On Sun, Apr 18, 2010 at 1:38 AM, Tom Herbert <therbert@...gle.com> wrote:
> That's cool!, but I still like the idea that this hash is treated as
> an opaque value getting the hash from the device to avoid the jhash
> or cache misses on the packet can also be a win...  Maybe connection
> tracking/firewall could use the skb->rxhash which provides the
> consistency and also eliminates the need to do more jhashes.
>

consistent rxhash only adds the risk of the hash collision, and I
don't think it is a big problem. For connection tracking/firewall use,
I am afraid that we have to recompute this value after defrag.  So we
have to export the hash function we used in RPS.

As NIC's hash function can be changed dynamically, the rxhash isn't
consistent, so the rxhash can't be used by connection tracking, socket
lookup and others come later.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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