Date: Fri, 17 Apr 2009 06:43:28 +0000 From: Pegasus Mc Cleaft <ken@mthelicon.com> To: freebsd-current@freebsd.org Subject: Re: [patch] zfs livelock and thread priorities Message-ID: <200904170643.28862.ken@mthelicon.com> In-Reply-To: <7DEF7288-1304-4A64-8A23-BB03349653EA@wanderview.com> References: <DC9F2088-A0AF-467D-8574-F24A045ABD81@wanderview.com> <ed91d4a80904142135n429dea52o672abf51116fa707@mail.gmail.com> <7DEF7288-1304-4A64-8A23-BB03349653EA@wanderview.com>
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On Friday 17 April 2009 01:30:21 Ben Kelly wrote: > On Apr 15, 2009, at 12:35 AM, Artem Belevich wrote: > > I'll give it a try in a few days. I'll let you know how it went. > > Just FYI, I was able to reproduce some of the failures with the > original patch using an SMP vmware image. The new patch seems to fix > these problems and I was able to successfully mount a zfs pool. > > > BTW, now that you're tinkering with ZFS threads and priorities, whould > > you by any chance have any idea why zfs scrub is so painfully slow on > > -current? > > When I start scrub on my -stable box, it pretty much runs full speed > > -- I can see disks under load all the time. > > However on -current scrub seems to run in small bursts. Disks get busy > > for a second or so and then things get quiet for about five seconds or > > so and this pattern repeats over and over. > > I don't know. I haven't had to scrub my devices very often. I ran a > couple here locally and did not see the behavior you describe. There > is a significant delay between typing zpool scrub and when it actually > begins disk I/O, but after that it completes without pause. If I get > a chance I'll try to look at what the scrub code is doing. Hi Ben, I saw the same pausing of of a scrub on my machine as Artem is. It may be coincidence, but I had disabled the zil and prefetch. After I re-enabled the zil and prefetch, the pausing stopped and the scrub would complete without any stalling. I never disabled the zil and prefetch to see if this was the true cause or not.. Peg
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