Date: Sat, 23 Dec 2006 14:00:33 +1300 From: Mark Kirkwood <markir@paradise.net.nz> To: Bruce Evans <bde@zeta.org.au> Cc: freebsd-performance@FreeBSD.org Subject: Re: Cached file read performance Message-ID: <458C7FB1.9020002@paradise.net.nz> In-Reply-To: <20061222171431.L18486@delplex.bde.org> References: <458B3651.8090601@paradise.net.nz> <20061222171431.L18486@delplex.bde.org>
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Bruce Evans wrote: > > None was attached. > (meaning the c prog yes?) I notice that it is stripped out from the web archive... so here's a link: http://homepages.paradise.net.nz/markir/download/freebsd/readtest.c >> Machines >> ======== >> - ufs2 32k blocksize, 4K fragments > ^^^^^^^^^^^^^^^^^^ > > Try using an unpessimized block size. Block sizes larger than BKVASIZE > (default 16K) fragment the buffer cache virtual memory. Right - I should have said, I saw a comment to that effect in src/sys/sys/param.h, and so I tested with 8K, 16K too, interestingly on my system 32K seemed to be faster, even for the bigger files (of course - hard to know if it was really significant...). > However, I > couldn't see much difference between block sizes of 16, 32 and 64K for > a small (32MB) md-malloced file system with a simple test program. > All versions got nearly 1/4 of bandwidth of main memory (800MB/S +-10% > an an AthlonXP with ~PC3200 memory). Cheers Mark
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