"High" cpu usage when using ZFS cache device

Christer Solskogen
Mon, 15 Nov 2010 21:13:47 -0000

My load on my i7 920 is certainly higher when I add a 8GB usb stick as
a ZFS cache device.
It seems to use about 10% system load - If I remove the cache device
it drops about 10%. Anyone else seeing this?

With cache device:
CPU:  0.0% user,  0.0% nice,  10.3% system,  0.0% interrupt, 91.5% idle
Mem: 822M Active, 9101M Inact, 1542M Wired, 34M Cache, 1237M Buf, 375M Free
Swap: 8192M Total, 200K Used, 8192M Free

Without:



         up 56+01:04:25  21:50:01
137 processes: 1 running, 136 sleeping
CPU:  0.1% user,  0.0% nice,  0.0% system,  0.0% interrupt, 99.9% idle
Mem: 822M Active, 9101M Inact, 1542M Wired, 34M Cache, 1237M Buf, 375M Free

The load reported by top is +0.50 with, and  +0.00 without.

FreeBSD 8.1-RELEASE amd64

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chs,