Messages in this thread | | | Date | Wed, 7 Nov 2012 17:17:30 +0100 | From | Jan Kara <> | Subject | Re: Debugging system freezes on filesystem writes |
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On Fri 02-11-12 04:19:24, Marcus Sundman wrote: > On 01.11.2012 21:01, Jan Kara wrote: > >On Mon 29-10-12 00:39:46, Marcus Sundman wrote: > > Hello, > > > >>I have a big problem with the system freezing and would appreciate > >>any help on debugging this and pinpointing where exactly the problem > >>is, so it could be fixed. > >> > >>So, whenever I write to the disk the system comes to a crawl or > >>freezes altogether. This happens even when the writing processes are > >>running on nice '19' and ionice 'idle'. (E.g. a 10 second compile > >>could freeze the system for several minutes, rendering the computer > >>pretty much unusable for anything interesting.) > >> > >>Here you can see a 20 second gap even in superhigh priority: > >># nice -n -20 ionice -c1 iostat -t -m -d -x 1 > http://pastebin.com/j5qnh2VV > >> > >>I'm currently running 3.5.0-17-lowlatency on the ZenBook UX31E, > >>using the NOOP I/O scheduler on the SanDisk SSD U100. The chipset > >>seems to be Intel QS67. I've had this same problem on 3.2.0 generic > >>and lowlatency kernels. > > These are Ubuntu kernels. Any chance to reproduce the issue with vanilla > >kernels - i.e. kernels without any Ubuntu patches? > > I'm afraid it's going to take a week to compile a kernel with this > freezing going on, but I suppose I could get another computer to do > the compiling. Or should I install some pre-compiled version? If so, > which one? You can install anything precompiled. It's just that I want to rule out some Ubuntu specific patches...
> >Also when you speak of > >system freezing - can you e.g. type to terminal while the system is frozen? > >Or is it just that running commands freezes? > > Typing usually doesn't work very well. It works for a word or two > and then stops working for a while and if I continue to type then > when it resumes only the last few characters appears. Typing in the > console is a bit better than in a terminal in X (not counting the > several minutes it can take to switch to the console (Ctrl-Alt-F1)). I see.
> Also, and this might be important, according to iotop there is > almost no disk writing going on during the freeze. (Occasionally > there are a few MB/s, but mostly it's 0-200 kB/s.) Well, at least > when an iotop running on nice -20 hasn't frozen completely, which it > does during the more severe freezes. OK, it seems as if your machine has some problems with memory allocations. Can you capture /proc/vmstat before the freeze and after the freeze and send them for comparison. Maybe it will show us what is the system doing.
Also you can try doing: echo never >/sys/kernel/mm/transparent_hugepage/enabled and see whether it changes anything.
Honza -- Jan Kara <jack@suse.cz> SUSE Labs, CR
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