Btw. the stall should be preceded by the OOM killer invocation. Could you share the OOM report please. I am asking because such an OOM killer would be clearly pre-mature as per your meminfo. I am trying to change that code and seeing your numbers might help me.
Thanks! On Wed 14-12-16 11:17:43, Michal Hocko wrote: > On Tue 13-12-16 18:11:01, David Arendt wrote: > > Hi, > > > > I receive the following page allocation stall while copying lots of > > large files from one btrfs hdd to another. > > > > Dec 13 13:04:29 server kernel: kworker/u16:8: page allocation stalls for > > 12260ms, order:0, mode:0x2400840(GFP_NOFS|__GFP_NOFAIL) > > Dec 13 13:04:29 server kernel: CPU: 0 PID: 24959 Comm: kworker/u16:8 > > Tainted: P O 4.9.0 #1 > [...] > > Dec 13 13:04:29 server kernel: Call Trace: > > Dec 13 13:04:29 server kernel: [<ffffffff813f3a59>] ? dump_stack+0x46/0x5d > > Dec 13 13:04:29 server kernel: [<ffffffff81114fc1>] ? > > warn_alloc+0x111/0x130 > > Dec 13 13:04:33 server kernel: [<ffffffff81115c38>] ? > > __alloc_pages_nodemask+0xbe8/0xd30 > > Dec 13 13:04:33 server kernel: [<ffffffff8110de74>] ? > > pagecache_get_page+0xe4/0x230 > > Dec 13 13:04:33 server kernel: [<ffffffff81323a8b>] ? > > alloc_extent_buffer+0x10b/0x400 > > Dec 13 13:04:33 server kernel: [<ffffffff812ef8c5>] ? > > btrfs_alloc_tree_block+0x125/0x560 > > OK, so this is > find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL) > > The main question is whether this really needs to be NOFS request... > > > Dec 13 13:04:33 server kernel: [<ffffffff8132442f>] ? > > read_extent_buffer_pages+0x21f/0x280 > > Dec 13 13:04:33 server kernel: [<ffffffff812d81f1>] ? > > __btrfs_cow_block+0x141/0x580 > > Dec 13 13:04:33 server kernel: [<ffffffff812d87b0>] ? > > btrfs_cow_block+0x100/0x150 > > Dec 13 13:04:33 server kernel: [<ffffffff812dc1d9>] ? > > btrfs_search_slot+0x1e9/0x9c0 > > Dec 13 13:04:33 server kernel: [<ffffffff8131ead2>] ? > > __set_extent_bit+0x512/0x550 > > Dec 13 13:04:33 server kernel: [<ffffffff812e1ab5>] ? > > lookup_inline_extent_backref+0xf5/0x5e0 > > Dec 13 13:04:34 server kernel: [<ffffffff8131f0a4>] ? > > set_extent_bit+0x24/0x30 > > Dec 13 13:04:34 server kernel: [<ffffffff812e4334>] ? > > update_block_group.isra.34+0x114/0x380 > > Dec 13 13:04:34 server kernel: [<ffffffff812e4694>] ? > > __btrfs_free_extent.isra.35+0xf4/0xd20 > > Dec 13 13:04:34 server kernel: [<ffffffff8134d561>] ? > > btrfs_merge_delayed_refs+0x61/0x5d0 > > Dec 13 13:04:34 server kernel: [<ffffffff812e8bd2>] ? > > __btrfs_run_delayed_refs+0x902/0x10a0 > > Dec 13 13:04:34 server kernel: [<ffffffff812ec0f0>] ? > > btrfs_run_delayed_refs+0x90/0x2a0 > > Dec 13 13:04:34 server kernel: [<ffffffff812ec384>] ? > > delayed_ref_async_start+0x84/0xa0 > > What would cause the reclaim recursion? > > > Dec 13 13:04:34 server kernel: Mem-Info: > > Dec 13 13:04:34 server kernel: active_anon:20 inactive_anon:34 > > isolated_anon:0\x0a active_file:7370032 inactive_file:450105 > > isolated_file:320\x0a unevictable:0 dirty:522748 writeback:189 > > unstable:0\x0a slab_reclaimable:178255 slab_unreclaimable:124617\x0a > > mapped:4236 shmem:0 pagetables:1163 bounce:0\x0a free:38224 free_pcp:241 > > free_cma:0 > > This speaks for itself. There is a lot of dirty data, basically no > anonymous memory and GFP_NOFS cannot do much to reclaim obviously. This > is either a configuraion bug as somebody noted down the thread (setting > the dirty_ratio) or suboptimality of the btrfs code which might request > NOFS even though it is not strictly necessary. This would be more for > btrfs developers. > -- > Michal Hocko > SUSE Labs -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
