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Date: Tue, 11 Oct 2011 10:16:02 -0700
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From: Artem Belevich <art@freebsd.org>
To: Steven Hartland <killing@multiplay.co.uk>
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Cc: =?ISO-8859-1?Q?Micka=EBl_Maillot?= <mickael.maillot@gmail.com>,
	Christer Solskogen <christer.solskogen@gmail.com>,
	freebsd-stable@freebsd.org, Ivan Voras <ivoras@freebsd.org>,
	Jeremy Chadwick <freebsd@jdc.parodius.com>
Subject: Re: "High" cpu usage when using ZFS cache device
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On Tue, Oct 11, 2011 at 2:34 AM, Steven Hartland
<killing@multiplay.co.uk> wrote:
> ----- Original Message ----- From: "Micka=EBl Maillot"
> <mickael.maillot@gmail.com>
>
>
>> same problem here after ~ 30 days with a production server and 2 SSD Int=
el
>> 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.

--Artem