Messages in this thread | | | Date | Tue, 24 Mar 2009 08:32:16 +0100 | From | Jesper Krogh <> | Subject | Re: Linux 2.6.29 |
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David Rees wrote: > On Mon, Mar 23, 2009 at 11:19 PM, Jesper Krogh <jesper@krogh.cc> wrote: >> I know this has been discussed before: >> >> [129401.996244] INFO: task updatedb.mlocat:31092 blocked for more than 480 >> seconds. > > Ouch - 480 seconds, how much memory is in that machine, and how slow > are the disks?
The 480 secondes is not the "wait time" but the time gone before the message is printed. It the kernel-default it was earlier 120 seconds but thats changed by Ingo Molnar back in september. I do get a lot of less noise but it really doesn't tell anything about the nature of the problem.
The systes spec: 32GB of memory. The disks are a Nexsan SataBeast with 42 SATA drives in Raid10 connected using 4Gbit fibre-channel. I'll let it up to you to decide if thats fast or slow?
The strange thing is actually that the above process (updatedb.mlocate) is writing to / which is a device without any activity at all. All activity is on the Fibre Channel device above, but process writing outsid that seems to be effected as well.
> What's your vm.dirty_background_ratio and > vm.dirty_ratio set to?
2.6.29-rc8 defaults: jk@hest:/proc/sys/vm$ cat dirty_background_ratio 5 jk@hest:/proc/sys/vm$ cat dirty_ratio 10
>> Consensus seems to be something with large memory machines, lots of dirty >> pages and a long writeout time due to ext3. > > All filesystems seem to suffer from this issue to some degree. I > posted to the list earlier trying to see if there was anything that > could be done to help my specific case. I've got a system where if > someone starts writing out a large file, it kills client NFS writes. > Makes the system unusable: > http://marc.info/?l=linux-kernel&m=123732127919368&w=2
Yes, I've hit 120s+ penalties just by saving a file in vim.
> Only workaround I've found is to reduce dirty_background_ratio and > dirty_ratio to tiny levels. Or throw good SSDs and/or a fast RAID > array at it so that large writes complete faster. Have you tried the > new vm_dirty_bytes in 2.6.29?
No.. What would you suggest to be a reasonable setting for that?
> Everyone seems to agree that "autotuning" it is the way to go. But no > one seems willing to step up and try to do it. Probably because it's > hard to get right!
I can test patches.. but I'm not a kernel-developer.. unfortunately.
Jesper
-- Jesper
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