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Date:      Tue, 11 Oct 2011 10:40:37 -0700
From:      Artem Belevich <art@freebsd.org>
To:        Steven Hartland <killing@multiplay.co.uk>
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
Message-ID:  <CAFqOu6jUzcHrZ=wT3xxaZYUd3aQERndHbPX2Kvxy=Vk1KkryEg@mail.gmail.com>
In-Reply-To: <E8A49AB737A64476892290B5866595C4@multiplay.co.uk>
References:  <AANLkTinzwyhABYxzWknzRFzLCbcDSd3BU2kQ5tX_SSk-@mail.gmail.com> <20101116003029.GC79816@numachi.com> <AANLkTinfTgXzf7t3PtO2VAef7NSkKWc0RnGdpv=6_-Vj@mail.gmail.com> <ibtqvp$bfq$1@dough.gmane.org> <AANLkTi=tJ-Hf%2BrMqG0=tEzNV2jJW-B_7Yu_ftW4tAMqT@mail.gmail.com> <20101116125431.GA90475@icarus.home.lan> <AANLkTi=mAWYCnWbWbX9B9fa05iyC_pivu08v-%2BbOf75f@mail.gmail.com> <AANLkTi=p9U6gK=Z5GyrAEzU2tDqbx%2ByWY=4eTZ5-0CuF@mail.gmail.com> <AANLkTi=XwO0RrU9uY5CF5p%2Bb9co1yneXX7UR2JsF55bL@mail.gmail.com> <AANLkTiknP4D5aayotFQ1jFpmov9Vv50GnFdVaXXs39rL@mail.gmail.com> <AANLkTikjd5CgcC3TEhLYuBXGukP0mUCyHtY-FwfYqs1K@mail.gmail.com> <852472071289497FA806928D0B41D0FE@multiplay.co.uk> <CAFqOu6i507j1tksV7xDYXsgUhQfp=JiKSXVnQHqM3ZQWyozG6A@mail.gmail.com> <E8A49AB737A64476892290B5866595C4@multiplay.co.uk>

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On Tue, Oct 11, 2011 at 10:21 AM, Steven Hartland
<killing@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.

--Artem



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