From owner-freebsd-stable@FreeBSD.ORG Fri Apr 11 21:02:09 2008 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 59AA3106566B for ; Fri, 11 Apr 2008 21:02:09 +0000 (UTC) (envelope-from karl@FS.denninger.net) Received: from FS.denninger.net (wsip-70-169-168-7.pn.at.cox.net [70.169.168.7]) by mx1.freebsd.org (Postfix) with ESMTP id D01B68FC13 for ; Fri, 11 Apr 2008 21:02:08 +0000 (UTC) (envelope-from karl@FS.denninger.net) Received: from fs.denninger.net (localhost [127.0.0.1]) by FS.denninger.net (8.14.2/8.13.1) with SMTP id m3BL1uNM090429 for ; Fri, 11 Apr 2008 16:01:56 -0500 (CDT) (envelope-from karl@FS.denninger.net) Received: from fs.denninger.net [127.0.0.1] by Spamblock-sys (LOCAL); Fri Apr 11 16:01:56 2008 Received: (from karl@localhost) by FS.denninger.net (8.14.2/8.13.1/Submit) id m3BL1uP4090426 for freebsd-stable@freebsd.org; Fri, 11 Apr 2008 16:01:56 -0500 (CDT) (envelope-from karl) Date: Fri, 11 Apr 2008 16:01:56 -0500 From: Karl Denninger To: freebsd-stable@freebsd.org Message-ID: <20080411210156.GA89281@FS.denninger.net> Mail-Followup-To: freebsd-stable@freebsd.org References: <20080410223153.GA336@FS.denninger.net> <20080411093316.GA31354@voi.aagh.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080411093316.GA31354@voi.aagh.net> User-Agent: Mutt/1.4.2.1i Organization: Karl's Sushi and Packet Smashers X-Die-Spammers: Spammers cheerfully broiled for supper and served with ketchup! Subject: Re: Disk I/O Question 7.0-STABLE 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: Fri, 11 Apr 2008 21:02:09 -0000 On Fri, Apr 11, 2008 at 10:33:16AM +0100, Thomas Hurst wrote: > * Karl Denninger (karl@denninger.net) wrote: > > > I have disks on the internal ICH7 adapters (on the motherboard), SATA, > > and also a TWE controller with two disks. > > > > When hitting the TWE controller hard I can hose the I/O performance on > > the primary (onboard) adapter quite severely to the point that it > > seriously impairs the system's overall performance. "systat -vm" > > shows the primary channels going to 100% busy but the transaction and > > I/O rate count is not all that high. The twe disk I am hammering, of > > course, is saturated (and blowing data at a high rate of speed - > > 70MBps+) > > I see exactly the same behavior on a dual dual core AMD box using amr(4) > (8 port LSI MegaRAID SATA) and an 8 port Marvell 88SX6081 ata(4) > controller. I have 3 RAID-1 arrays configured on the LSI and a single > drive on the Marvell; I can freeze up IO to all of them for several > seconds just by running find / >/dev/null for up to 30s. > > gstat shows the IO queue for one drive in the high hundreds (all > writes), and it seems waiting for it to flush is what kills the rest of > the system. > > My best guess is this is a result of the syncer flushing atime updates. > I should try mounting my /usr noatime and seeing if the problem goes > away. Not the greatest of solutions, but meh. Mounting with noatime does help a bit but does NOT prevent the problem from showing up. Note that softupdates is OFF on the disk that is being hammered when everything goes to hell so its not a buffer flushing problem there either. -- -- Karl Denninger (karl@denninger.net) Internet Consultant & Kids Rights Activist http://www.denninger.net My home on the net - links to everything I do! http://scubaforum.org Your UNCENSORED place to talk about DIVING! http://genesis3.blogspot.com Musings Of A Sentient Mind