Date: Tue, 16 Nov 2010 16:53:57 +0100 From: Christer Solskogen <christer.solskogen@gmail.com> To: Ollivier Robert <roberto@keltia.freenix.fr> Cc: freebsd-stable@freebsd.org Subject: Re: "High" cpu usage when using ZFS cache device Message-ID: <AANLkTi=2kNM1aoNds_CuHEnNnYQ4sDk3NPvxVuk_cUB6@mail.gmail.com> In-Reply-To: <20101116131128.GB21229@rron.local> 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>
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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}
--
chs,
help
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