On Wed, Dec 04, 2013 at 10:52:18AM +0900, Joonsoo Kim wrote: > On Tue, Dec 03, 2013 at 04:59:10PM -0800, Andrew Morton wrote: > > On Tue, 8 Oct 2013 16:58:10 -0400 Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > > > > Buffer allocation has a very crude indefinite loop around waking the > > > flusher threads and performing global NOFS direct reclaim because it > > > can not handle allocation failures. > > > > > > The most immediate problem with this is that the allocation may fail > > > due to a memory cgroup limit, where flushers + direct reclaim might > > > not make any progress towards resolving the situation at all. Because > > > unlike the global case, a memory cgroup may not have any cache at all, > > > only anonymous pages but no swap. This situation will lead to a > > > reclaim livelock with insane IO from waking the flushers and thrashing > > > unrelated filesystem cache in a tight loop. > > > > > > Use __GFP_NOFAIL allocations for buffers for now. This makes sure > > > that any looping happens in the page allocator, which knows how to > > > orchestrate kswapd, direct reclaim, and the flushers sensibly. It > > > also allows memory cgroups to detect allocations that can't handle > > > failure and will allow them to ultimately bypass the limit if reclaim > > > can not make progress. > > > > Problem. > > > > > --- a/fs/buffer.c > > > +++ b/fs/buffer.c > > > @@ -1005,9 +1005,19 @@ grow_dev_page(struct block_device *bdev, sector_t block, > > > struct buffer_head *bh; > > > sector_t end_block; > > > int ret = 0; /* Will call free_more_memory() */ > > > + gfp_t gfp_mask; > > > > > > - page = find_or_create_page(inode->i_mapping, index, > > > - (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); > > > + gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS; > > > + gfp_mask |= __GFP_MOVABLE; > > > > https://bugzilla.kernel.org/show_bug.cgi?id=65991 > > > > WARNING: CPU: 0 PID: 1 at mm/page_alloc.c:1539 get_page_from_freelist+0x8a9/0x8c0() > > Modules linked in: > > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-rc1 #42 > > Hardware name: Acer Aspire 7750G/JE70_HR, BIOS V1.07 03/02/2011 > > 0000000000000009 ffff8801c6121650 ffffffff81898d39 0000000000000000 > > ffff8801c6121688 ffffffff8107dc43 0000000000000002 0000000000000001 > > 0000000000284850 0000000000000000 ffff8801cec04680 ffff8801c6121698 > > Call Trace: > > [<ffffffff81898d39>] dump_stack+0x4e/0x7a > > [<ffffffff8107dc43>] warn_slowpath_common+0x73/0x90 > > [<ffffffff8107dd15>] warn_slowpath_null+0x15/0x20 > > [<ffffffff81116f69>] get_page_from_freelist+0x8a9/0x8c0 > > [<ffffffff81330cdd>] ? trace_hardirqs_off_thunk+0x3a/0x3c > > [<ffffffff81117070>] __alloc_pages_nodemask+0xf0/0x770 > > [<ffffffff81330cdd>] ? trace_hardirqs_off_thunk+0x3a/0x3c > > [<ffffffff81156823>] kmemcheck_alloc_shadow+0x53/0xf0 > > [<ffffffff81152495>] new_slab+0x345/0x3e0 > > [<ffffffff81897712>] __slab_alloc.isra.57+0x215/0x535 > > [<ffffffff81328030>] ? __radix_tree_preload+0x60/0xf0 > > [<ffffffff811545c8>] kmem_cache_alloc+0x118/0x150 > > [<ffffffff81328030>] ? __radix_tree_preload+0x60/0xf0 > > [<ffffffff81328030>] __radix_tree_preload+0x60/0xf0 > > [<ffffffff81328125>] radix_tree_maybe_preload+0x25/0x30 > > [<ffffffff8110faf7>] add_to_page_cache_locked+0x37/0x100 > > [<ffffffff8110fbd5>] add_to_page_cache_lru+0x15/0x40 > > [<ffffffff8110ff37>] find_or_create_page+0x57/0x90 > > [<ffffffff8118e630>] __getblk+0xf0/0x2f0 > > > > That __GFP_NOFAIL is getting down into > > radix_tree_preload->kmem_cache_alloc() and I expect that in its > > boundless stupidity, slab has decided to inappropriately go and use an > > unnecessarily massive page size for radix_tree_node_cachep's underlying > > memory allocations. So we end up using GFP_NOFAIL for an order=2 (or > > more) allocation, which is unacceptably risky, methinks. > > > > I really really wish slab wouldn't do this. The benefit is surely very > > small and these unnecessary higher-order allocations are quite abusive > > of the page allocator. > > > > Can we please make slab stop doing this? > > > > radix_tree_nodes are 560 bytes and the kernel often allocates them in > > times of extreme memory stress. We really really want them to be > > backed by order=0 pages. > > Hello, Andrew. > > Following patch would fix this problem. > > Thanks. > > -------------------8<------------------------ > >From 7f21232d1eeffccdbd0f6d79c04d297cf95a713e Mon Sep 17 00:00:00 2001 > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > Date: Wed, 4 Dec 2013 10:36:11 +0900 > Subject: [PATCH] slub: fix high order page allocation problem with > __GFP_NOFAIL > > SLUB already try to allocate high order page with clearing __GFP_NOFAIL. > But, when allocating shadow page for kmemcheck, it missed clearing > the flag. This trigger WARN_ON_ONCE() reported by Christian Casteyde. > > https://bugzilla.kernel.org/show_bug.cgi?id=65991 > > This patch fix this situation by using same allocation flag as original > allocation. > > Reported-by: Christian Casteyde <casteyde.christian@xxxxxxx> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > diff --git a/mm/slub.c b/mm/slub.c > index 545a170..3dd28b1 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1335,11 +1335,12 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > page = alloc_slab_page(alloc_gfp, node, oo); > if (unlikely(!page)) { > oo = s->min; > + alloc_gfp = flags; > /* > * Allocation may have failed due to fragmentation. > * Try a lower order alloc if possible > */ > - page = alloc_slab_page(flags, node, oo); > + page = alloc_slab_page(alloc_gfp, node, oo); > > if (page) > stat(s, ORDER_FALLBACK); > @@ -1349,7 +1350,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) { > int pages = 1 << oo_order(oo); > > - kmemcheck_alloc_shadow(page, oo_order(oo), flags, node); > + kmemcheck_alloc_shadow(page, oo_order(oo), alloc_gfp, node); > > /* > * Objects from caches that have a constructor don't get > -- > 1.7.9.5 Hello, Pekka and Christoph. Could you review this patch? I think that we should merge it to fix the problem reported by Christian. Thanks. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
