On Sun, Sep 05, 2010 at 09:45:54PM +0800, Wu Fengguang wrote: > [restoring CC list] > > On Sun, Sep 05, 2010 at 09:14:47PM +0800, Dave Chinner wrote: > > On Sun, Sep 05, 2010 at 02:05:39PM +0800, Wu Fengguang wrote: > > > On Sun, Sep 05, 2010 at 10:15:55AM +0800, Dave Chinner wrote: > > > > On Sun, Sep 05, 2010 at 09:54:00AM +0800, Wu Fengguang wrote: > > > > > Dave, could you post (publicly) the kconfig and /proc/vmstat? > > > > > > > > > > I'd like to check if you have swap or memory compaction enabled.. > > > > > > > > Swap is enabled - it has 512MB of swap space: > > > > > > > > $ free > > > > total used free shared buffers cached > > > > Mem: 4054304 100928 3953376 0 4096 43108 > > > > -/+ buffers/cache: 53724 4000580 > > > > Swap: 497976 0 497976 > > > > > > It looks swap is not used at all. > > > > It isn't 30s after boot, abut I haven't checked after a livelock. > > That's fine. I see in your fs_mark-wedge-1.png that there are no > read/write IO at all when CPUs are 100% busy. So there should be no > swap IO at "livelock" time. > > > > > And memory compaction is not enabled: > > > > > > > > $ grep COMPACT .config > > > > # CONFIG_COMPACTION is not set > > Memory compaction is not likely the cause too. It will only kick in for > order > 3 allocations. > > > > > > > > > The .config is pretty much a 'make defconfig' and then enabling XFS and > > > > whatever debug I need (e.g. locking, memleak, etc). > > > > > > Thanks! The problem seems hard to debug -- you cannot login at all > > > when it is doing lock contentions, so cannot get sysrq call traces. > > > > Well, I don't know whether it is lock contention at all. The sets of > > traces I have got previously have shown backtraces on all CPUs in > > direct reclaim with several in draining queues, but no apparent lock > > contention. > > That's interesting. Do you still have the full backtraces? > > Maybe your system eats too much slab cache (icache/dcache) by creating > so many zero-sized files. The system may run into problems reclaiming > so many (dirty) slab pages. Yes, that's where most of the memory pressure is coming from. However, it's not stuck reclaiming slab - it's pretty clear from another chart that I run that the slab cache contents is not changing aross the livelock. IOWs, it appears to get stuck before it gets to shrink_slab(). Worth noting, though, is that XFS metadata workloads do create page cache pressure as well - all the metadata pages are cached on a separate address space, so perhaps it is getting stuck there... > > > How about enabling CONFIG_LOCK_STAT? Then you can check > > > /proc/lock_stat when the contentions are over. > > > > Enabling the locking debug/stats gathering slows the workload > > by a factor of 3 and doesn't produce the livelock.... > > Oh sorry.. but it would still be interesting to check the top > contended locks for this workload without any livelocks :) I'll see what i can do. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>