"High" cpu usage when using ZFS cache device

Artem Belevich art at freebsd.org
Tue Oct 11 17:40:38 UTC 2011

On Tue, Oct 11, 2011 at 10:21 AM, Steven Hartland
<killing at multiplay.co.uk> wrote:
> Thanks for the confirmation there Artem, we currently can't use 8-STABLE
> due to the serious routing issue, seem like every packet generates a
> RTM_MISS routing packet to be sent, which causes high cpu load.
> Thread: "Re: serious packet routing issue causing ntpd high load?"

It's a bummer. If you can build your own kernel cherry-picking
following revisions may help with long-term stability:
r218429 - fixes original overflow causing CPU hogging by l2arc feeding
thread. It will keep you up and running for longer until you hit
another overflow. If I remember correctly, it will hit you around
100-days of uptime.

Following changes were done after ZFSv28 import, so they will not
apply directly to 8-RELEASE, but the idea applies to ZFSv15 as well.
The changes should be easy to backport.

r223412 - avoids more early overflows in time routines.
r224647 - avoids time overflow in TXG processing.


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