Date: Tue, 16 Nov 2010 13:15:32 +0100 From: Christer Solskogen <christer.solskogen@gmail.com> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-stable@freebsd.org Subject: Re: "High" cpu usage when using ZFS cache device Message-ID: <AANLkTi=tJ-Hf%2BrMqG0=tEzNV2jJW-B_7Yu_ftW4tAMqT@mail.gmail.com> In-Reply-To: <ibtqvp$bfq$1@dough.gmane.org> References: <AANLkTinzwyhABYxzWknzRFzLCbcDSd3BU2kQ5tX_SSk-@mail.gmail.com> <20101116003029.GC79816@numachi.com> <AANLkTinfTgXzf7t3PtO2VAef7NSkKWc0RnGdpv=6_-Vj@mail.gmail.com> <ibtqvp$bfq$1@dough.gmane.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Nov 16, 2010 at 12:47 PM, Ivan Voras <ivoras@freebsd.org> wrote: > You can easily test it - use the stick as a simple disk device with UFS and > see how much CPU does it take simply to talk to the device. 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. See: CPU: 0.0% user, 0.0% nice, 0.6% system, 0.0% interrupt, 99.3% idle Mem: 832M Active, 960M Inact, 7017M Wired, 2600K Cache, 1237M Buf, 3063M Free Swap: 8192M Total, 8192M Free PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND 38261 root 1 46 0 5776K 1112K wdrain 7 0:07 4.98% dd But when using it as cache device for zfs: CPU: 0.0% user, 0.0% nice, 11.9% system, 0.0% interrupt, 88.1% idle Mem: 832M Active, 193M Inact, 5782M Wired, 2592K Cache, 1237M Buf, 5066M Free Swap: 8192M Total, 8192M Free The funny thing is that when I add the device (and some cache is added to it) the load is normal. But the load goes up when nothing is written to it (or beeing read from it) -- chs,
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?AANLkTi=tJ-Hf%2BrMqG0=tEzNV2jJW-B_7Yu_ftW4tAMqT>