Date: Tue, 16 Nov 2010 14:00:48 +0100 From: Christer Solskogen <christer.solskogen@gmail.com> To: Alexander Leidinger <Alexander@leidinger.net> Cc: freebsd-stable@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: "High" cpu usage when using ZFS cache device Message-ID: <AANLkTimbtw-vnTwsywm2eeGK2qcAxggSA9ACL0HrufZm@mail.gmail.com> In-Reply-To: <20101116135557.66601irt6kd1gndw@webmail.leidinger.net> References: <AANLkTinzwyhABYxzWknzRFzLCbcDSd3BU2kQ5tX_SSk-@mail.gmail.com> <20101116003029.GC79816@numachi.com> <AANLkTinfTgXzf7t3PtO2VAef7NSkKWc0RnGdpv=6_-Vj@mail.gmail.com> <ibtqvp$bfq$1@dough.gmane.org> <AANLkTi=tJ-Hf%2BrMqG0=tEzNV2jJW-B_7Yu_ftW4tAMqT@mail.gmail.com> <20101116135557.66601irt6kd1gndw@webmail.leidinger.net>
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On Tue, Nov 16, 2010 at 1:55 PM, Alexander Leidinger
<Alexander@leidinger.net> wrote:
> How do you measure that nothing is read or written to it?
>
I used zpool iostat -v
> Please check with
> =A0gstat -f '^<DEVICE>$'
> if there are really no reads/writes to the device (please replace <DEVICE=
>
> with the name of your USB device, e.g. da0).
>
> If you see writes, I would say
> =A0- this is the reason for the load
> =A0- your cache is on the way to be filled with
> =A0 useful data
>
I see almost no writes (nor reads)
> If gstat shows zero activity, I suggest to run 'top -S' and look at the
> process(es) which consume about 10% CPU (do not take care about the idle
> process). Based upon this we can maybe suggest further things to
> investigate.
>
Heres the output of that:
CPU: 0.0% user, 0.0% nice, 11.8% system, 0.0% interrupt, 88.1% idle
Mem: 841M Active, 193M Inact, 5086M Wired, 4876K Cache, 1237M Buf, 5750M Fr=
ee
Swap: 8192M Total, 8192M Free
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAN=
D
11 root 8 171 ki31 0K 128K CPU0 0 ??? 713.62% idle
5 root 5 -8 - 0K 76K zvol:i 5 401.9H 91.16% zfsker=
n
Thanks for your time on looking into this :-)
--=20
chs,
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