Date: Thu, 09 Aug 2012 18:39:35 +0300 From: Daniel Kalchev <daniel@digsys.bg> To: freebsd-fs@freebsd.org Subject: ZFS scrub CPU bound? Message-ID: <5023D9B7.20001@digsys.bg>
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I have built myself an server with SSD only drives. That thing goes "fast", like during scrub # zpool status pool: system state: ONLINE scan: scrub in progress since Thu Aug 9 18:30:46 2012 87.1G scanned out of 193G at 602M/s, 0h3m to go 0 repaired, 45.06% done config: NAME STATE READ WRITE CKSUM system ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 da0p3 ONLINE 0 0 0 da1p3 ONLINE 0 0 0 da2p3 ONLINE 0 0 0 da3p3 ONLINE 0 0 0 But, what I wonder is top -S # top -S last pid: 7912; load averages: 9.89, 3.26, 1.29 up 0+06:03:59 18:32:04 146 processes: 3 running, 142 sleeping, 1 waiting CPU: 0.4% user, 0.0% nice, 51.4% system, 0.8% interrupt, 47.3% idle Mem: 2171M Active, 1541M Inact, 5407M Wired, 25M Cache, 416K Buf, 22G Free Swap: 8192M Total, 8192M Free PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND 11 root 32 155 ki31 0K 512K CPU31 31 190.2H 1818.46% idle 0 root 268 -8 0 0K 4288K - 0 141:25 1261.33% kernel 4 root 4 -8 - 0K 80K CPU30 30 9:13 95.17% zfskern 13 root 3 -8 - 0K 48K - 4 5:37 42.97% geom 12 root 66 -84 - 0K 1056K WAIT 0 6:19 30.86% intr [...] It seems that zfskern will top to 100%. This is an 32 core system, and as you see scrub, at 600MB/sec is able to eat 16 cores (from 2x 2.2 GHz Opteron 6274). There is high load on geom as well... but geom does go over 100% CPU, so I suppose it scales. What might be there in ZFS code that is single-CPU bound? freebsd 9-stable. Daniel
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