From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:41825 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753485Ab3LPLpi (ORCPT ); Mon, 16 Dec 2013 06:45:38 -0500 Date: Mon, 16 Dec 2013 19:45:27 +0800 From: Liu Bo To: Filipe David Manana Cc: "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH] Btrfs: fix very slow inode eviction and fs unmount Message-ID: <20131216114525.GD30413@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <1384900175-30031-1-git-send-email-fdmanana@gmail.com> <20131216092707.GB30413@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Mon, Dec 16, 2013 at 11:05:31AM +0000, Filipe David Manana wrote: > On Mon, Dec 16, 2013 at 9:27 AM, Liu Bo wrote: > > On Tue, Nov 19, 2013 at 10:29:35PM +0000, Filipe David Borba Manana wrote: > >> 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 > >> > > > > What about the time of umount after 'sync'? > > Same huge difference. > Thanks. Not seeing that huge one with the latest btrfs, maybe because your memory is rather larger. time sync FSSync '/mnt/btrfs' real 0m17.006s user 0m0.004s sys 0m0.056s time umount /mnt/btrfs real 0m0.910s user 0m0.003s sys 0m0.715s -liubo > > > > > The following ext4 uses sync while btrfs uses 'btrfs filesystem sync'. > > > > I don't think they are the same thing. > > > > -liubo > > > >> 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 > >> --- > >> 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 5a5de36..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)) { > >> -- > >> 1.7.9.5 > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > >> the body of a message to majordomo@vger.kernel.org > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > -- > Filipe David Manana, > > "Reasonable men adapt themselves to the world. > Unreasonable men adapt the world to themselves. > That's why all progress depends on unreasonable men."