On Fri, 11 Jan 2013 22:51:35 +1100 paul.szabo@xxxxxxxxxxxxx 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>