netdev - Re: small RPS cache for fragments?

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Message-Id: <20110517.164732.2145088965289526395.davem@davemloft.net>
Date:	Tue, 17 May 2011 16:47:32 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: small RPS cache for fragments?

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 17 May 2011 22:14:48 +0200

> OK but do we have workloads actually needing this optimization at all ?

Yes, I've seen performance graphs where RPS/RFS falls off the cliff
when datagram sizes go from 1024 to 2048 bytes.

Wrt. defrag queue overhead, it still is minor compared to the cost of
processing 1/2 of all packets on one cpu on a 24 core system.

BTW, if we can steer reliably, we could make per-cpu defrag queue if
you worry about it so much :-)
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