Messages in this thread | | | Date | Tue, 10 Apr 2012 12:26:28 +1000 | From | Dave Chinner <> | Subject | Re: dramatic I/O slowdown after upgrading 2.6.32->3.0 |
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On Fri, Apr 06, 2012 at 08:45:40AM +0400, Michael Tokarev wrote: > On 06.04.2012 03:29, Jan Kara wrote: > > > On Fri 30-03-12 20:50:54, Michael Tokarev wrote: > >> I'm observing a dramatic slowdown of several hosts after upgrading > >> from 2.6.32.y to 3.0.x i686 kernels (in both cases from kernel.org, > >> on both cases the last version is relatively latest). > [] > >> What's the way to debug this issue? > > Identifying a particular kernel where things regresses might help as Jon > > wrote. Just from top of my head, 3.0 had a bug in device plugging so > > readahead was broken. I think it was addressed in -stable series so you > > That's definitely not readahead, it since writes are painfully slow > too. I found one more example -- extlinux --once="test kernel" with > 3.0 takes about 20 seconds to complete on an idle system. > > > might want to check out latest 3.0-stable. > > I did mention this in my initial email (that part quoted above) -- > both 2.6.32 and 3.0 are relatively latest from each series, > right now it is 3.0.27. > > Yesterday I tried to do some bisection, but ended up in an unbootable > system (it is remote production server), so now I'm waiting for remote > hands to repair it (I don't yet know what went wrong, we'll figure it > out). I've some time during nights when I can do anything with that > machine, but I have to keep it reachable/working on each reboot. > > Apparently I was wrong saying that there's another machine which > suffers from the same issue -- nope, the other machine had an unrelated > issue which I fixed. So it turns out that from about 200 different > machines, I've just one machine which does not run 3.0 kernel properly. > I especially tried 3.0 on a few more - different - machines last > weekend, in order to see what other machines has this problem, but > found nothing. > > So I'll try to continue (or actually _start_) the bisection on this > very server, the way it will be possible having in mind the difficult > conditions. > > I just thoght I'd ask first, maybe someone knows offhand what may be > the problem.. ;)
Barriers. Turn them off, and see if that fixes your problem.
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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