Date: Thu, 28 Aug 2003 10:19:55 -0700 From: Sean Chittenden <seanc@FreeBSD.org> To: Robert Watson <rwatson@freebsd.org>, Bill Moran <wmoran@potentialtech.com>, freebsd-database@freebsd.org, freebsd-fs@freebsd.org, freebsd-performance@freebsd.org Subject: Re: Some additional tests run on my performance testing Message-ID: <20030828171955.GE83759@perrin.nxad.com> In-Reply-To: <20030828085947.GA41090@HAL9000.homeunix.com> References: <3F4D5957.8000204@potentialtech.com> <Pine.NEB.3.96L.1030827225030.29532F-100000@fledge.watson.org> <20030828085947.GA41090@HAL9000.homeunix.com>
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> > Did you look at any of the blocksize-related patches that have > > been floating around? > > I tried his tests on a stock pgsql 7.3.4, twice with an 8K block > filesystem and twice with a 16K block UFS2 filesystem and measured > an improvement of about 4% for the 8K filesystem. (Take this cum > grano salis though, since this was an informal test and I don't have > enough data to draw a statistically significant conclusion.) It > turns out that the tables in Bill's tests have no indices, so pgsql > winds up doing practically nothing but sequential reads and > sequential writes of entire tables. A more typical database load > would probably be characterized by mostly random access patterns and > possibly more synchronous writes to the WAL log. For the sake of eating my own advice and in an attempt to verify the numbers you suggest above, I loaded a DB with 8k and 16K blocks (translation: almost all write activities). With 8K blocks: 15.188u 3.404s 7:12.27 4.2% 209+340k 1251+0io 0pf+0w 14.867u 3.686s 7:32.54 4.0% 201+327k 1252+0io 0pf+0w avg wall clock sec to complete: 442 With 16K blocks: 15.192u 3.312s 6:44.43 4.5% 198+322k 1253+0io 0pf+0w 15.120u 3.330s 6:51.43 4.4% 205+334k 1254+0io 0pf+0w avg wall clock sec to complete: 407 Which is different than what your results suggest, but I'll take the 35sec/8% speedup any day of the week and twice on Sunday. Granted these tests were done on my laptop and were 100% write, I'd expect them to stay about the same across the board. If someone wants to do some good read tests, I'd be interested in those results. -sc -- Sean Chittenden
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