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Date:      Wed, 28 Nov 2001 14:15:10 -0800
From:      Luigi Rizzo <luigi@FreeBSD.org>
To:        Peter Wemm <peter@wemm.org>
Cc:        cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/pci if_sis.c
Message-ID:  <20011128141510.A13586@iguana.aciri.org>
In-Reply-To: <20011128211641.5FF9E3808@overcee.netplex.com.au>
References:  <200111281610.fASGAcU63381@freefall.freebsd.org> <20011128211641.5FF9E3808@overcee.netplex.com.au>

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> While this helps things like packet forwarding, it hurts things like

and generic servers (web, proxies) where things are done in
userland and the content is opaque and the only unaligned
accesses are for the IP/TCP headers (but those are touched
already in the packet forwarding case).

> NFS which now have to do lots and lots of unaligned accesses.

I would actually like to see some numbers showing that this is the
case.  Where else these unaligned accesses could be other than in
creating the NFS/RPC headers ? Do a bunch of unaligned accesses
really cost more than a memory-to-memory copy of 1500 bytes ?

> Have you benchmarked anything else besides packet forwarding?

no, how would you benchmark this (that is without hitting a
bottleneck elsewhere in the system) ?

> >   Right now the new behaviour is controlled by a sysctl variable,
> >   hw.sis_quick which defaults to 1 (on), you can set it to 0 to
...
> 
> Please do not remove this yet.

no problem. It will actually be useful to tell people who have
a reasonable testbed to toggle this and see if it makes a difference.

	cheers
	luigi
----------------------------------+-----------------------------------------
 Luigi RIZZO, luigi@iet.unipi.it  . ACIRI/ICSI (on leave from Univ. di Pisa)
 http://www.iet.unipi.it/~luigi/  . 1947 Center St, Berkeley CA 94704
 Phone: (510) 666 2927
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