Date: Fri, 22 Dec 2006 10:08:12 +0800 From: David Xu <davidxu@freebsd.org> To: Mark Kirkwood <markir@paradise.net.nz> Cc: freebsd-performance@freebsd.org Subject: Re: Cached file read performance Message-ID: <458B3E0C.6090104@freebsd.org> In-Reply-To: <458B3651.8090601@paradise.net.nz> References: <458B3651.8090601@paradise.net.nz>
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Mark Kirkwood wrote: > I recently did some testing on the performance of cached reads using two > (almost identical) systems, one running FreeBSD 6.2PRE and the other > running Gentoo Linux - the latter acting as a control. I initially > started a thread of the same name on -stable, but it was suggested I > submit a mail here. > > My background for wanting to examine this is that I work with developing > database software (postgres internals related) and cached read > performance is pretty important - since we typically try hard to > encourage cached access whenever possible. > > Anyway on to the results: I used the attached program to read a cached > 781MB file sequentially and randomly with a specified block size (see > below). The conclusion I came to was that our (i.e FreeBSD) cached read > performance (particularly for smaller block sizes) could perhaps be > improved... now I'm happy to help in any way - the machine I've got > running STABLE can be upgraded to CURRENT in order to try out patches > (or in fact to see if CURRENT is faster at this already!)... > > Best wishes > > Mark > I suspect in such a test, memory copying speed will be a key factor, I don't have number to back up my idea, but I think Linux has lots of tweaks, such as using MMX instruction to copy data. Regards, David Xu
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