Date: Tue, 30 Aug 2011 23:18:15 +0400 From: Lev Serebryakov <lev@FreeBSD.org> To: freebsd-fs@freebsd.org Subject: Very inconsistent (read) speed on UFS2 Message-ID: <317753422.20110830231815@serebryakov.spb.ru> In-Reply-To: <1945418039.20110830231024@serebryakov.spb.ru> References: <1945418039.20110830231024@serebryakov.spb.ru>
next in thread | previous in thread | raw e-mail | index | archive | help
Hello, Freebsd-fs. You wrote 30 =E0=E2=E3=F3=F1=F2=E0 2011 =E3., 23:10:24: SORRY FOR SENDING INCOMPLETE MESSAGE! Now, when I "defragmented" my large FS, I see very inconsistent read speeds on same files. Is it Ok? My setup is: (1) FreeBSD 8.2-STABLE/x64 (2) E4400 CPU, 2GiB RAM (3) 5xHDDs in RAID5 (software), controller is ICH9R. (4) UFS2 with 32KiB block, vfs.read_max=3D32 (1MiB read-ahead). (5) System and swap on another (6th) HDD, but swap is unused. (6) No periodic or background processes access FS in question at all. Simple program reads each of 12 files (460MiB each) 15 times in cycle like 01, 02, ..., 12, 01,... so, cache in memory should be thrashed, as reading process returns to same data every ~5.5GiB and here are only 2GiB physical memory in system. And speed of these reads are VERY inconsistent. I've calculated min/average/max and standard deviation and results are like this: Name Min/Avg/Max StdDev r012f02.nef 120/235/413 MiB/s 83 r012f09.nef 154/248/393 MiB/s 80 r012f12.nef 106/212/293 MiB/s 63 r012f05.nef 86/206/280 MiB/s 62 r012f08.nef 128/223/332 MiB/s 60 r012f11.nef 155/257/327 MiB/s 56 r012f03.nef 121/213/279 MiB/s 52 r012f10.nef 120/226/284 MiB/s 45 r012f07.nef 121/199/249 MiB/s 41 r012f01.nef 135/199/242 MiB/s 33 It is results from 15 runs! One time file was read at sustained average speed 120MiB/s (~3.8 seconds) and next time it was 413MiB/s (only ~1.1 second!) And it is not case when first read is slowest. No. Sometimes last one is slowest, for example. Is it Ok? I'm very disappointed to see 120MiB/s when I know that hardware can give 415MiB/s, but something strange slows down the process. --=20 // Black Lion AKA Lev Serebryakov <lev@FreeBSD.org>
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?317753422.20110830231815>