"High" cpu usage when using ZFS cache device

Christer Solskogen christer.solskogen at gmail.com
Tue Nov 16 15:53:58 UTC 2010

On Tue, Nov 16, 2010 at 2:11 PM, Ollivier Robert
<roberto at keltia.freenix.fr> wrote:
> According to Christer Solskogen:
>> See, that is why I think it is a ZFS issue. Because I did that.
>> I created a UFS filesystem on the same usb stick. Mounted it and did a
>> "dd if=/dev/zero of=/mnt/file".
>> The systemload goes +0.6 instead if +10.3.
> Do not forget that everything that is read/written from/to USB devices goes through the CPU (no DMA or anything for USB devices).

I didn't forget that. Thats why I also tested with UFS. And I do not
have the same issue with that.

With top -HS I discovered this:
    5 root        -8    -     0K    76K zio->i  4 403.2H 85.06%


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