Messages in this thread | | | Date | Fri, 11 Jan 2013 12:31:49 -0800 | From | Andrew Morton <> | Subject | Re: [RFC] Reproducible OOM with partial workaround |
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On Fri, 11 Jan 2013 22:51:35 +1100 paul.szabo@sydney.edu.au wrote:
> Dear Andrew, > > > Check /proc/slabinfo, see if all your lowmem got eaten up by buffer_heads. > > Please see below: I do not know what any of that means. This machine has > been running just fine, with all my users logging in here via XDMCP from > X-terminals, dozens logged in simultaneously. (But, I think I could make > it go OOM with more processes or logins.)
I'm counting 107MB in slab there. Was this dump taken when the system was at or near oom?
Please send a copy of the oom-killer kernel message dump, if you still have one.
> > If so, you *may* be able to work around this by setting > > /proc/sys/vm/dirty_ratio really low, so the system keeps a minimum > > amount of dirty pagecache around. Then, with luck, if we haven't > > broken the buffer_heads_over_limit logic it in the past decade (we > > probably have), the VM should be able to reclaim those buffer_heads. > > I tried setting dirty_ratio to "funny" values, that did not seem to > help.
Did you try setting it as low as possible?
> Did you notice my patch about bdi_position_ratio(), how it was > plain wrong half the time (for negative x)?
Nope, please resend.
> Anyway that did not help. > > > Alternatively, use a filesystem which doesn't attach buffer_heads to > > dirty pages. xfs or btrfs, perhaps. > > Seems there is also a problem not related to filesystem... or rather, > the essence does not seem to be filesystem or caches. The filesystem > thing now seems OK with my patch doing drop_caches.
hm, if doing a regular drop_caches fixes things then that implies the problem is not with dirty pagecache. Odd.
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