Date: Mon, 24 May 2004 14:01:47 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Kevin Oberman <oberman@es.net> Cc: freebsd-current@freebsd.org Subject: Re: Disk performance under CURRENT Message-ID: <Pine.NEB.3.96L.1040524135406.98946D-100000@fledge.watson.org> In-Reply-To: <20040524161726.DC2305D08@ptavv.es.net>
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On Mon, 24 May 2004, Kevin Oberman wrote:
> Sorry, but I've been off-line for a while on travel. And my wireless
> card died. :-(
>
> In any case, by kernel is built without witness, so I get sysctl:
> unknown oid 'debug.witness_watch'. The system is a UP P4-M and not
> running APIC. No INVARIANTS, either.
Could you investigate the following possible areas to explore?
(1) Could you see if the ATA configuration differs between the two
versions, especially relating to DMA mode. There are substantial ATA
driver changes, so it could be different parameters are being used.
(2) Could you investigate how the performance difference changes with
block size? In particular, I would expect the performance difference
to be most visible with small block sizes, and least visible with
large block sizes. I think before you used a 256k block size, which I
would classify as on the larger side, but it would be interesting to
see a table like the following fleshed out:
4.x 5.x
1 byte
256 bytes
512 bytes
1k
2k
4k
8k
16k
32k
64k
128k
256k
512k
1m
For each, a sustained transfer of at least 30 seconds would be good.
(3) Could you run systat -vmstat, iostat, or some other variation during
the benchmark and determine the levels of system, interrupt, user, and
idle CPU during the benchmark.
(4) I don't know much about the machine you're running on, but could you
try compiling a kernel without SMP and see what difference that makes,
if any?
Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org Senior Research Scientist, McAfee Research
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