netdev - Re: [PATCH v2] ipv4: Early TCP socket demux.

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Message-Id: <20120619.214657.1345825814176201681.davem@davemloft.net>
Date:	Tue, 19 Jun 2012 21:46:57 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...tta.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v2] ipv4: Early TCP socket demux.

From: Stephen Hemminger <shemminger@...tta.com>
Date: Tue, 19 Jun 2012 19:35:49 -0700

> Any benchmark numbers?

Measuring the path from ip_rcv_finish() to where we lock the socket in
tcp_v4_rcv(), on a SPARC-T3, with a pre-warmed routing cache:

Both sk and RT lookup:	~4200 cycles
Optimized early demux:	~2800 cycles

These numbers can be decreased further, because since we're already
looking at the TCP header we can pre-cook the TCP control block in the
SKB and skip much of the stuff that tcp_v4_rcv() does since we've done
it already in the early demux code.

> I think the number of ref count operations per packet is going to be
> the next line in the sand.

There is only one, for the socket.  We haven't taken a reference on the
route for years.
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