Date: Tue, 16 Nov 2010 08:01:50 -0800 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Christer Solskogen <christer.solskogen@gmail.com> Cc: freebsd-stable@freebsd.org Subject: Re: "High" cpu usage when using ZFS cache device Message-ID: <20101116160150.GA93581@icarus.home.lan> In-Reply-To: <AANLkTi=2kNM1aoNds_CuHEnNnYQ4sDk3NPvxVuk_cUB6@mail.gmail.com> 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> <20101116131128.GB21229@rron.local> <AANLkTi=2kNM1aoNds_CuHEnNnYQ4sDk3NPvxVuk_cUB6@mail.gmail.com>
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On Tue, Nov 16, 2010 at 04:53:57PM +0100, Christer Solskogen wrote:
> On Tue, Nov 16, 2010 at 2:11 PM, Ollivier Robert
> <roberto@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%
> {l2arc_feed_threa}
Please provide the output from:
sysctl -a | grep vfs.zfs.arc
sysctl -a | grep vm.kmem
sysctl kstat.zfs.misc.arcstats
Thank you.
--
| Jeremy Chadwick jdc@parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |
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