Date: Tue, 15 Jul 2008 10:11:42 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Steve Bertrand <steve@ibctech.ca> Cc: freebsd-stable@freebsd.org Subject: Re: taskqueue timeout Message-ID: <200807151711.m6FHBgVO007481@apollo.backplane.com> References: <487CCD46.8080506@ibctech.ca>
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:Hi everyone, : :I'm wondering if the problems described in the following link have been :resolved: : :http://unix.derkeiler.com/Mailing-Lists/FreeBSD/stable/2008-02/msg00211.html : :I've got four 500GB SATA disks in a ZFS raidz pool, and all four of them :are experiencing the behavior. : :The problem only happens with extreme disk activity. The box becomes :unresponsive (can not SSH etc). Keyboard input is displayed on the :console, but the commands are not accepted. : :Is there anything I can do to either figure this out, or work around it? : :Steve If you are getting DMA timeouts, go to this URL: http://wiki.freebsd.org/JeremyChadwick/ATA_issues_and_troubleshooting Then I would suggest going into /usr/src/sys/dev/ata (I think, on FreeBSD), locate all instances where request->timeout is set to 5, and change them all to 10. cd /usr/src/sys/dev/ata fgrep 'request->timeout' *.c ... change all assignments of 5 to 10 ... Try that first. If it helps then it is a known issue. Basically a combination of the on-disk write cache and possible ECC corrections, remappings, or excessive remapped sectors can cause the drive to take much longer then normal to complete a request. The default 5-second timeout is insufficient. If it does help, post confirmation to prod the FBsd developers to change the timeouts. -- If you are NOT getting DMA timeouts then the ZFS lockups may be due to buffer/memory deadlocks. ZFS has knobs for adjusting its memory footprint size. Lowering the footprint ought to solve (most of) those issues. It's actually somewhat of a hard issue to solve. Filesystems like UFS aren't complex enough to require the sort of dynamic memory allocations deep in the filesystem that ZFS and HAMMER need to do. -Matt Matthew Dillon <dillon@backplane.com>
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