From owner-svn-src-all@FreeBSD.ORG Tue Oct 12 20:22:17 2010 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5073A106566C; Tue, 12 Oct 2010 20:22:17 +0000 (UTC) (envelope-from ben@wanderview.com) Received: from mail.wanderview.com (mail.wanderview.com [66.92.166.102]) by mx1.freebsd.org (Postfix) with ESMTP id EB3D78FC0A; Tue, 12 Oct 2010 20:22:16 +0000 (UTC) Received: from xykon.in.wanderview.com (xykon.in.wanderview.com [10.76.10.152]) (authenticated bits=0) by mail.wanderview.com (8.14.4/8.14.4) with ESMTP id o9CJjEeA030636 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Tue, 12 Oct 2010 19:45:14 GMT (envelope-from ben@wanderview.com) Mime-Version: 1.0 (Apple Message framework v1081) Content-Type: text/plain; charset=us-ascii From: Ben Kelly In-Reply-To: <201004151634.o3FGY7wX053198@svn.freebsd.org> Date: Tue, 12 Oct 2010 15:45:14 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <0168690D-7294-48FE-8223-1E3343CCC802@wanderview.com> References: <201004151634.o3FGY7wX053198@svn.freebsd.org> To: Pawel Jakub Dawidek X-Mailer: Apple Mail (2.1081) X-Spam-Score: -1.01 () ALL_TRUSTED,T_RP_MATCHES_RCVD X-Scanned-By: MIMEDefang 2.68 on 10.76.20.1 Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r206665 - head/sys/geom/eli X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Oct 2010 20:22:17 -0000 On Apr 15, 2010, at 12:34 PM, Pawel Jakub Dawidek wrote: > Author: pjd > Date: Thu Apr 15 16:34:06 2010 > New Revision: 206665 > URL: http://svn.freebsd.org/changeset/base/206665 >=20 > Log: > Use lower priority for GELI worker threads. This improves system > responsiveness under heavy GELI load. Sorry to reply to such an old commit, but I wanted to note that this = causes a regression on my server. It is probably fairly specific to my = setup, so it may not make sense to fix, but I thought I should at least = let you know. My server is an old i386 with a zfs pool on top of a geli partition. = When under heavy disk load the zfs subsystem can enter a message passing = loop between the txg and zio threads until any queued disk i/o is = flushed. With the geli worker threads at a lower priority this can lead = to livelock since geli never gets scheduled to perform the flush. =46rom = my previous debugging efforts I believe this can only be triggered if = the ARC is under heavy pressure and the processor is near, or at, 100% = CPU utilization. Here is the old thread on this issue: = http://old.nabble.com/-patch--zfs-livelock-and-thread-priorities-td2258702= 2.html On my local system I have simply reverted this change and bumped up the = priority on the geli worker threads to PVM to match the priority used by = the zio threads. Before doing this I could reliably trigger the = livelock by running my backup process. Anyway, its not clear to me what a good general purpose solution would = be. I just wanted to note the issue in case anyone else encounters it. Thanks. - Ben=