"High" cpu usage when using ZFS cache device

Artem Belevich art at freebsd.org
Tue Oct 11 17:37:50 UTC 2011

On Tue, Oct 11, 2011 at 2:34 AM, Steven Hartland
<killing at multiplay.co.uk> wrote:
> ----- Original Message ----- From: "Mickaël Maillot"
> <mickael.maillot at gmail.com>
>> same problem here after ~ 30 days with a production server and 2 SSD Intel
>> X25M as L2.
>> so we update and reboot the 8-STABLE server every month.
> Old thread but also seeing this on 8.2-RELEASE so looks like this
> may still be an issue.
> In our case this machine was running mysql with 2 x 60GB cache
> SSD's. I checked for usage when the machine was idle just before
> reboot to fix and the l2arc thread was still using 100% of a core
> even with no disk access happening.
> Was a PR ever raised for this?

No, there was no PR.

L2arc CPU hogging after ~24 days was fixed in r218180 in -HEAD and was
MFC'ed to 8-stable in r218429 early in February '11.

If you're using 8-RELEASE, upgrading to 8-STABLE would be something to
consider as there were other ZFS-related issues fixed there that
didn't make it into -RELEASE.


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