Date: Tue, 12 Oct 2010 15:45:14 -0400 From: Ben Kelly <ben@wanderview.com> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r206665 - head/sys/geom/eli Message-ID: <0168690D-7294-48FE-8223-1E3343CCC802@wanderview.com> In-Reply-To: <201004151634.o3FGY7wX053198@svn.freebsd.org> References: <201004151634.o3FGY7wX053198@svn.freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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=
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?0168690D-7294-48FE-8223-1E3343CCC802>