From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:46934 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753045Ab3LPL50 (ORCPT ); Mon, 16 Dec 2013 06:57:26 -0500 Date: Mon, 16 Dec 2013 19:57:14 +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: <20131216115711.GE30413@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <1384900175-30031-1-git-send-email-fdmanana@gmail.com> <20131216092707.GB30413@localhost.localdomain> <20131216114525.GD30413@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 11:48:08AM +0000, Filipe David Manana wrote: > On Mon, Dec 16, 2013 at 11:45 AM, Liu Bo wrote: > > 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. > > Not sure if I understand you. > Latest btrfs-next has this change integrated. Was the test below with > it integrated? You would have to compare it with a build without this > change. I'm testing the script with Chris's upstream repo, not btrfs-next, and umount is normal. It's possible that some patches merged in btrfs-next make umount's latency longer than expected. thanks, -liubo > > Thanks. > > > > > 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." > > > > -- > 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."