>From: Dieter <free...@sopwith.solgatos.com> >Subject: Re: A specific example of a disk i/o problem >To: freebsd-performance@freebsd.org >Date: Friday, October 2, 2009, 1:07 AM > >Updated demo, just to make sure: > ># big_file is larger than main memory, on same disk as man (/usr) >time man de # get baseline time for man command without >competing i/o >cat big_file > /dev/null # flush man command and data from memory >cat big_file > /dev/null & # generate i/o, attempt to use up bottleneck >time man de # see how much longer man takes with competing >i/o
Trying it on something that surely will have i/o issues: PIII 500 w/ 60 GB PATA drive and 128 MB RAM. Blank minimal install + man pages right now. I'm trying with a "file /etc/" command instead of trying to reliably time man... It seems the file command always hits the disk. This should also make any sort of "flushing" unecessary, shouldn't it? liebnitz# uname -a FreeBSD xyz 7.2-RELEASE FreeBSD 7.2-RELEASE #0: Fri May 1 08:49:13 UTC 2009 r...@walker.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386 liebnitz# time dd if=/dev/zero of=/usr/bigfile count=4096 bs=1M 4096+0 records in 4096+0 records out 4294967296 bytes transferred in 363.700967 secs (11809062 bytes/sec) 0.055u 83.971s 6:03.78 23.0% 25+1071k 128+34391io 0pf+0w liebnitz# time file /etc/ [run 5 times] 4.052u 0.047s 0:04.14 98.7% 15+1085k 0+0io 0pf+0w 4.068u 0.031s 0:04.13 99.0% 16+1095k 0+0io 0pf+0w 4.052u 0.046s 0:04.13 99.0% 16+1101k 0+0io 0pf+0w 4.044u 0.054s 0:04.13 99.0% 16+1092k 0+0io 0pf+0w 4.052u 0.046s 0:04.13 99.0% 15+1091k 0+0io 0pf+0w Ok, so that looks pretty repeatable. Now... liebnitz# cat /usr/bigfile > /dev/null & [1] 37923 liebnitz# time file /etc/* [again run 5 times] 4.146u 0.038s 0:06.80 61.3% 15+1103k 87+0io 8pf+0w 4.128u 0.054s 0:06.73 61.9% 15+1095k 93+0io 6pf+0w Flush as example. liebnitz# cat /usr/bigfile > /dev/null liebnitz# cat /usr/bigfile > /dev/null & [1] 37890 _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org"
