On Mon, 23 Aug 2010, Wu Fengguang wrote: > > I've been testing parallel create workloads over the weekend, and > > I've seen this a couple of times now under 8 thread parallel creates > > with XFS. I'm running on an 8p VM with 4GB RAM and a fast disk > > subsystem. Basically I am seeing the create rate drop to zero > > with all 8 CPUs stuck spinning for up to 2 minutes. 'echo t > > > /proc/sysrq-trigger' while this is occurring gives the following > > trace for all the fs-mark processes: > > > > [49506.624018] fs_mark R running task 0 8376 7917 0x00000008 > > [49506.624018] 0000000000000000 ffffffff81b94590 00000000000008fc 0000000000000002 > > [49506.624018] 0000000000000000 0000000000000286 0000000000000297 ffffffffffffff10 > > [49506.624018] ffffffff810b3d02 0000000000000010 0000000000000202 ffff88011df777a8 > > [49506.624018] Call Trace: > > [49506.624018] [<ffffffff810b3d02>] ? smp_call_function_many+0x1a2/0x210 > > [49506.624018] [<ffffffff810b3ce5>] ? smp_call_function_many+0x185/0x210 > > [49506.624018] [<ffffffff81109170>] ? drain_local_pages+0x0/0x20 > > [49506.624018] [<ffffffff810b3d92>] ? smp_call_function+0x22/0x30 > > [49506.624018] [<ffffffff810849a4>] ? on_each_cpu+0x24/0x50 > > [49506.624018] [<ffffffff81107bec>] ? drain_all_pages+0x1c/0x20 > > [49506.624018] [<ffffffff8110825a>] ? __alloc_pages_nodemask+0x57a/0x730 > > [49506.624018] [<ffffffff8113c6d2>] ? kmem_getpages+0x62/0x160 > > [49506.624018] [<ffffffff8113d2b2>] ? fallback_alloc+0x192/0x240 > > [49506.624018] [<ffffffff8113cce1>] ? cache_grow+0x2d1/0x300 > > [49506.624018] [<ffffffff8113d04a>] ? ____cache_alloc_node+0x9a/0x170 > > [49506.624018] [<ffffffff8113cf6c>] ? cache_alloc_refill+0x25c/0x2a0 > > [49506.624018] [<ffffffff8113ddb3>] ? __kmalloc+0x193/0x230 > > [49506.624018] [<ffffffff812f59af>] ? kmem_alloc+0x8f/0xe0 > > [49506.624018] [<ffffffff812f59af>] ? kmem_alloc+0x8f/0xe0 > > [49506.624018] [<ffffffff812f5a9e>] ? kmem_zalloc+0x1e/0x50 > > [49506.624018] [<ffffffff812e2f4d>] ? xfs_log_commit_cil+0x9d/0x440 > > [49506.624018] [<ffffffff812eeec6>] ? _xfs_trans_commit+0x1e6/0x2b0 > > [49506.624018] [<ffffffff812f2b6f>] ? xfs_create+0x51f/0x690 > > [49506.624018] [<ffffffff812ffdb7>] ? xfs_vn_mknod+0xa7/0x1c0 > > [49506.624018] [<ffffffff812fff00>] ? xfs_vn_create+0x10/0x20 > > [49506.624018] [<ffffffff811510b8>] ? vfs_create+0xb8/0xf0 > > [49506.624018] [<ffffffff81151d2c>] ? do_last+0x4dc/0x5d0 > > [49506.624018] [<ffffffff81153bd7>] ? do_filp_open+0x207/0x5e0 > > [49506.624018] [<ffffffff8105fc58>] ? pvclock_clocksource_read+0x58/0xd0 > > [49506.624018] [<ffffffff8115eaca>] ? alloc_fd+0x10a/0x150 > > [49506.624018] [<ffffffff81144005>] ? do_sys_open+0x65/0x130 > > [49506.624018] [<ffffffff81144110>] ? sys_open+0x20/0x30 > > [49506.624018] [<ffffffff81036072>] ? system_call_fastpath+0x16/0x1b > > > > Eventually the problem goes away, and the system goes back to > > performing at the normal rate. Any ideas on how to avoid this > > problem? I'm using CONFIG_SLAB=y is that is relevant.... > > zone->lock contention? Try rip the following two lines. The change > might be a bit aggressive though :) > > Thanks, > Fengguang > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1bb327a..c08b8d3 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1864,9 +1864,6 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > > cond_resched(); > > - if (order != 0) > - drain_all_pages(); > - > if (likely(*did_some_progress)) > page = get_page_from_freelist(gfp_mask, nodemask, order, > zonelist, high_zoneidx, You may be interested in Mel's patchset that he just proposed for -mm which identifies watermark variations on machines with high cpu counts (perhaps even eight, as in this report). The last patch actually reworks this hunk of the code as well. http://marc.info/?l=linux-mm&m=128255044912938 http://marc.info/?l=linux-mm&m=128255045312950 http://marc.info/?l=linux-mm&m=128255045012942 http://marc.info/?l=linux-mm&m=128255045612954 Dave, it would be interesting to see if this fixes your problem. -- 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>