Date: Tue, 03 May 2005 07:37:58 +0300 From: Petri Helenius <pete@he.iki.fi> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance on 5.x Message-ID: <42770026.80901@he.iki.fi> In-Reply-To: <20050502214208.M87351@fledge.watson.org> References: <19879.1115061648@critter.freebsd.dk> <20050502214208.M87351@fledge.watson.org>
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Robert Watson wrote: > > The next thing that would be quite nice to measure is the rate of I/O > transactions per second we can get to the disk using the disk device > directly, with a minimal transaction size. I have a vague > recollection that you have to be careful in Linux because their > character device nodes for disk devices are buffered, and you really > want unbuffered I/O. I noticed that changing vfs.read_max from the default 8 to 16 has a dramatic effect on sequential read performance. Increasing it further did not have measurable effect. Pete
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