From owner-freebsd-stable@FreeBSD.ORG Mon Feb 8 16:17:40 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 4A2E11065670 for ; Mon, 8 Feb 2010 16:17:40 +0000 (UTC) (envelope-from mad@madpilot.net) Received: from megatron.madpilot.net (megatron.madpilot.net [88.149.173.206]) by mx1.freebsd.org (Postfix) with ESMTP id DB4448FC0A for ; Mon, 8 Feb 2010 16:17:39 +0000 (UTC) Received: from megatron.madpilot.net (localhost [127.0.0.1]) by megatron.madpilot.net (Postfix) with ESMTP id E1F4D1B2F; Mon, 8 Feb 2010 17:17:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=madpilot.net; h= user-agent:in-reply-to:content-disposition:content-type :content-type:mime-version:references:message-id:subject:subject :from:from:date:date:received:received; s=mail; t=1265645856; x= 1267460256; bh=QGlgENip+KbAxx3+twTJLTzChlFYK4BtthXxmouVPG8=; b=n bCKl9k5sD7cl0noLa4FMse8ouEspbCMNuYo/jniFPkZxwgpOQo9hEQ1vWUlK2EKL TauYMdTIZSoj6WP4dLG722kZKME8OMQ65lHtSogLebSYL6f+hnPyuANcQda6qpZr 6uDdpE4C9LzdfAzlJv/aoZYvfMQy+B3f8ph7XdX30g= X-Virus-Scanned: amavisd-new at madpilot.net Received: from megatron.madpilot.net ([127.0.0.1]) by megatron.madpilot.net (megatron.madpilot.net [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id aMLcyMzI3vHm; Mon, 8 Feb 2010 17:17:36 +0100 (CET) Received: by megatron.madpilot.net (Postfix, from userid 1000) id 199A41B28; Mon, 8 Feb 2010 17:17:36 +0100 (CET) Date: Mon, 8 Feb 2010 17:17:35 +0100 From: Guido Falsi To: Jeremy Chadwick Message-ID: <20100208161735.GB43063@megatron.madpilot.net> References: <20100208143329.GA12057@megatron.madpilot.net> <20100208145147.GA3733@icarus.home.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100208145147.GA3733@icarus.home.lan> X-Operating-System: FreeBSD 8.0-STABLE User-Agent: Mutt/1.5.20 (2009-06-14) Cc: freebsd-stable@freebsd.org Subject: Re: ATA_CAM + ZFS gives short 1-2 seconds system freeze on disk load 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: Mon, 08 Feb 2010 16:17:40 -0000 On Mon, Feb 08, 2010 at 06:51:47AM -0800, Jeremy Chadwick wrote: > On Mon, Feb 08, 2010 at 03:33:29PM +0100, Guido Falsi wrote: > > > > It gets very annoying and I don't remember this happening before > > activating the ATA_CAM flag. There was some slowdown with big disk > > access, but not a total freeze. > > This happens without ATA_CAM (e.g. using ataahci(4) or any other > controller driver). > > The behaviour you're describing (bursty heavy disk I/O that stalls the > subsystem) is pretty much the norm on all FreeBSD systems I've seen with > ZFS. When it starts happening, it's easy to notice/follow using "zpool > iostat 1" or "gstat -I500ms". Lots of I/O will happen (read or write) > and the ARC is essentially being thrashed -- said utilities won't show > any I/O counters incrementing until some threshold is reached, where > you'll see a massive amount of I/O reported, during which time the > system is sluggish (beyond acceptable levels, IMHO). A few seconds > later, the I/O counters start reporting 0 as the ARC gets used, then > a few seconds massive I/O, rinse lather repeat. > > I've seen Solaris 10 systems which behave the same way, and others which > don't. I don't know what causes things to start behaving this way. Thank you for the explanation. I in fact see the same problem with the legacy ata driver. I see this is something not trivial to fix, so I don't want to put too much burden on the pople who brought us zfs, which is anyway a great thing! Anyway the sluggish responsiveness of the system during these bursts is a problem for desktop use. I see that ZFS is mainly a server oriented FS, but this should be addressed sometime in the future I think. > > > BTW there's another thing that shows up on this machine. Lately, this > > too after putting the option ATA_CAM in the kernel, during boot there is > > a long pause(exactly one minute, as the message below states) in this > > point of the dmesg: > > This should probably be discussed in a different thread. I'll follow your suggestion and post a new thread about this. Thank you again! -- Guido Falsi