Date: Mon, 11 Mar 1996 08:56:26 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: jkh@time.cdrom.com (Jordan K. Hubbard) Cc: hackers@FreeBSD.ORG Subject: Re: Another wcarchive report.. Message-ID: <199603110756.IAA17954@labinfo.iet.unipi.it> In-Reply-To: <1529.826498452@time.cdrom.com> from "Jordan K. Hubbard" at Mar 10, 96 02:53:53 pm
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> I thought people would be amused to see the load at the >1000 user > scenario: > ... > Service class anonymous - 1012 users (1250 maximum) > > jkh@wcarchive-> top > load averages: 12.18, 9.51, 7.99 14:48:20 > 1128 processes:9 running, 1118 sleeping, 1 zombie > Cpu states: 13.5% user, 0.0% nice, 27.3% system, 19.9% interrupt, 39.4% idle > Memory: 307M Active, 2356K Inact, 50M Wired, 129M Cache, 676K Free > Swap: 819M Total, 804M Free, 2% Inuse > > PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND > 82 root 2 0 180K 268K sleep 300:12 2.71% 2.71% syslogd > 23487 root 2 0 464K 320K sleep 0:15 1.83% 1.83% ls > 22605 dave 2 0 7324K 7636K sleep 0:31 1.18% 1.18% perl > 28761 jkh 85 0 1464K 1596K run 0:00 2.19% 0.65% top > 28176 root 2 0 700K 460K sleep 0:00 0.54% 0.53% ftpd > 28775 root 2 0 592K 448K sleep 0:00 3.83% 0.53% ls > 28772 root 2 0 700K 440K sleep 0:00 2.31% 0.42% ftpd > 28773 root 2 0 680K 428K sleep 0:00 2.31% 0.42% ftpd > 28784 root 2 0 680K 424K sleep 0:00 8.59% 0.42% ftpd ... wcarchive (and similar extremely-busy systems) are undoubtably interesting patients to study. I am wondering: with such a busy system, I expect that performance is mostly limited by disk seeks. Is it possible that the relatively low load average is actually limited by the number of disks -- i.e. 1-2 processes per disk are ready, the other are just waiting for their I/O requests to complete ? This would also explain the "39.4% idle". It would be interesting to know the effective aggregate disk bandwidth (not the peak value, that's going to make us consumed with envy :) and see if that is the actual bottleneck. Also, is there some special tuning of parameters (say, reserve some memory for holding directories, modify ftpd to so some readahead depending on the actual speed of the connection, etc.) Luigi ==================================================================== Luigi Rizzo Dip. di Ingegneria dell'Informazione email: luigi@iet.unipi.it Universita' di Pisa tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ ====================================================================
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