From owner-freebsd-stable@FreeBSD.ORG Tue Nov 16 12:54:34 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 71B58106566C for ; Tue, 16 Nov 2010 12:54:34 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from QMTA11.westchester.pa.mail.comcast.net (qmta11.westchester.pa.mail.comcast.net [76.96.59.211]) by mx1.freebsd.org (Postfix) with ESMTP id 19C598FC0C for ; Tue, 16 Nov 2010 12:54:33 +0000 (UTC) Received: from omta11.westchester.pa.mail.comcast.net ([76.96.62.36]) by QMTA11.westchester.pa.mail.comcast.net with comcast id Xni41f0020mv7h05Bouatv; Tue, 16 Nov 2010 12:54:34 +0000 Received: from koitsu.dyndns.org ([98.248.41.155]) by omta11.westchester.pa.mail.comcast.net with comcast id XouZ1f0043LrwQ23XouZK1; Tue, 16 Nov 2010 12:54:34 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id CDFEA9B427; Tue, 16 Nov 2010 04:54:31 -0800 (PST) Date: Tue, 16 Nov 2010 04:54:31 -0800 From: Jeremy Chadwick To: Christer Solskogen Message-ID: <20101116125431.GA90475@icarus.home.lan> References: <20101116003029.GC79816@numachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: freebsd-stable@freebsd.org, Ivan Voras Subject: Re: "High" cpu usage when using ZFS cache device X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Nov 2010 12:54:34 -0000 On Tue, Nov 16, 2010 at 01:15:32PM +0100, Christer Solskogen wrote: > On Tue, Nov 16, 2010 at 12:47 PM, Ivan Voras 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) Since you're running 8.1-RELEASE, can you please test this issue on RELENG_8 (8.1-STABLE) and see if it exists there? You can download a livefs snapshot or equivalent and test via that (preferably one which has ZFS v15 support; you'll need to make a new pool rather than upgrade your existing pool, unless you plan on moving to RELENG_8 permanently). Here's such a snapshot: ftp://ftp4.freebsd.org/pub/FreeBSD/snapshots/201011/ -- | 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 |