From 131e404a2a54d30f894425ef723f9867a43bff4c Mon Sep 17 00:00:00 2001 From: Filipe David Borba Manana Date: Tue, 19 Nov 2013 22:29:35 +0000 Subject: [PATCH] Btrfs: fix very slow inode eviction and fs unmount The inode eviction can be very slow, because during eviction we tell the VFS to truncate all of the inode's pages. This results in calls to btrfs_invalidatepage() which in turn does calls to lock_extent_bits() and clear_extent_bit(). These calls result in too many merges and splits of extent_state structures, which consume a lot of time and cpu when the inode has many pages. In some scenarios I have experienced umount times higher than 15 minutes, even when there's no pending IO (after a btrfs fs sync). A quick way to reproduce this issue: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ cd /mnt/btrfs $ sysbench --test=fileio --file-num=128 --file-total-size=16G \ --file-test-mode=seqwr --num-threads=128 \ --file-block-size=16384 --max-time=60 --max-requests=0 run $ time btrfs fi sync . FSSync '.' real 0m25.457s user 0m0.000s sys 0m0.092s $ cd .. $ time umount /mnt/btrfs real 1m38.234s user 0m0.000s sys 1m25.760s The same test on ext4 runs much faster: $ mkfs.ext4 /dev/sdb3 $ mount /dev/sdb3 /mnt/ext4 $ cd /mnt/ext4 $ sysbench --test=fileio --file-num=128 --file-total-size=16G \ --file-test-mode=seqwr --num-threads=128 \ --file-block-size=16384 --max-time=60 --max-requests=0 run $ sync $ cd .. $ time umount /mnt/ext4 real 0m3.626s user 0m0.004s sys 0m3.012s After this patch, the unmount (inode evictions) is much faster: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ cd /mnt/btrfs $ sysbench --test=fileio --file-num=128 --file-total-size=16G \ --file-test-mode=seqwr --num-threads=128 \ --file-block-size=16384 --max-time=60 --max-requests=0 run $ time btrfs fi sync . FSSync '.' real 0m26.774s user 0m0.000s sys 0m0.084s $ cd .. $ time umount /mnt/btrfs real 0m1.811s user 0m0.000s sys 0m1.564s Signed-off-by: Filipe David Borba Manana Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/inode.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 84 insertions(+), 14 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5a5de36d..e889779 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -4488,6 +4488,62 @@ static int btrfs_setattr(struct dentry *dentry, struct iattr *attr) return err; } +/* + * While truncating the inode pages during eviction, we get the VFS calling + * btrfs_invalidatepage() against each page of the inode. This is slow because + * the calls to btrfs_invalidatepage() result in a huge amount of calls to + * lock_extent_bits() and clear_extent_bit(), which keep merging and splitting + * extent_state structures over and over, wasting lots of time. + * + * Therefore if the inode is being evicted, let btrfs_invalidatepage() skip all + * those expensive operations on a per page basis and do only the ordered io + * finishing, while we release here the extent_map and extent_state structures, + * without the excessive merging and splitting. + */ +static void evict_inode_truncate_pages(struct inode *inode) +{ + struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; + struct extent_map_tree *map_tree = &BTRFS_I(inode)->extent_tree; + struct rb_node *node; + + ASSERT(inode->i_state & I_FREEING); + truncate_inode_pages(&inode->i_data, 0); + + write_lock(&map_tree->lock); + while (!RB_EMPTY_ROOT(&map_tree->map)) { + struct extent_map *em; + + node = rb_first(&map_tree->map); + em = rb_entry(node, struct extent_map, rb_node); + remove_extent_mapping(map_tree, em); + free_extent_map(em); + } + write_unlock(&map_tree->lock); + + spin_lock(&io_tree->lock); + while (!RB_EMPTY_ROOT(&io_tree->state)) { + struct extent_state *state; + struct extent_state *cached_state = NULL; + + node = rb_first(&io_tree->state); + state = rb_entry(node, struct extent_state, rb_node); + atomic_inc(&state->refs); + spin_unlock(&io_tree->lock); + + lock_extent_bits(io_tree, state->start, state->end, + 0, &cached_state); + clear_extent_bit(io_tree, state->start, state->end, + EXTENT_LOCKED | EXTENT_DIRTY | + EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING | + EXTENT_DEFRAG, 1, 1, + &cached_state, GFP_NOFS); + free_extent_state(state); + + spin_lock(&io_tree->lock); + } + spin_unlock(&io_tree->lock); +} + void btrfs_evict_inode(struct inode *inode) { struct btrfs_trans_handle *trans; @@ -4498,7 +4554,8 @@ void btrfs_evict_inode(struct inode *inode) trace_btrfs_inode_evict(inode); - truncate_inode_pages(&inode->i_data, 0); + evict_inode_truncate_pages(inode); + if (inode->i_nlink && ((btrfs_root_refs(&root->root_item) != 0 && root->root_key.objectid != BTRFS_ROOT_TREE_OBJECTID) || @@ -7379,6 +7436,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset, struct extent_state *cached_state = NULL; u64 page_start = page_offset(page); u64 page_end = page_start + PAGE_CACHE_SIZE - 1; + int inode_evicting = inode->i_state & I_FREEING; /* * we have the page locked, so new writeback can't start, @@ -7394,17 +7452,21 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset, btrfs_releasepage(page, GFP_NOFS); return; } - lock_extent_bits(tree, page_start, page_end, 0, &cached_state); - ordered = btrfs_lookup_ordered_extent(inode, page_offset(page)); + + if (!inode_evicting) + lock_extent_bits(tree, page_start, page_end, 0, &cached_state); + ordered = btrfs_lookup_ordered_extent(inode, page_start); if (ordered) { /* * IO on this page will never be started, so we need * to account for any ordered extents now */ - clear_extent_bit(tree, page_start, page_end, - EXTENT_DIRTY | EXTENT_DELALLOC | - EXTENT_LOCKED | EXTENT_DO_ACCOUNTING | - EXTENT_DEFRAG, 1, 0, &cached_state, GFP_NOFS); + if (!inode_evicting) + clear_extent_bit(tree, page_start, page_end, + EXTENT_DIRTY | EXTENT_DELALLOC | + EXTENT_LOCKED | EXTENT_DO_ACCOUNTING | + EXTENT_DEFRAG, 1, 0, &cached_state, + GFP_NOFS); /* * whoever cleared the private bit is responsible * for the finish_ordered_io @@ -7428,14 +7490,22 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset, btrfs_finish_ordered_io(ordered); } btrfs_put_ordered_extent(ordered); - cached_state = NULL; - lock_extent_bits(tree, page_start, page_end, 0, &cached_state); + if (!inode_evicting) { + cached_state = NULL; + lock_extent_bits(tree, page_start, page_end, 0, + &cached_state); + } + } + + if (!inode_evicting) { + clear_extent_bit(tree, page_start, page_end, + EXTENT_LOCKED | EXTENT_DIRTY | + EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING | + EXTENT_DEFRAG, 1, 1, + &cached_state, GFP_NOFS); + + __btrfs_releasepage(page, GFP_NOFS); } - clear_extent_bit(tree, page_start, page_end, - EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC | - EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG, 1, 1, - &cached_state, GFP_NOFS); - __btrfs_releasepage(page, GFP_NOFS); ClearPageChecked(page); if (PagePrivate(page)) { -- 2.7.4