From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f47.google.com ([209.85.214.47]:54703 "EHLO mail-bk0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753045Ab3LPLFc (ORCPT ); Mon, 16 Dec 2013 06:05:32 -0500 Received: by mail-bk0-f47.google.com with SMTP id mx12so2257100bkb.20 for ; Mon, 16 Dec 2013 03:05:31 -0800 (PST) MIME-Version: 1.0 Reply-To: fdmanana@gmail.com In-Reply-To: <20131216092707.GB30413@localhost.localdomain> References: <1384900175-30031-1-git-send-email-fdmanana@gmail.com> <20131216092707.GB30413@localhost.localdomain> Date: Mon, 16 Dec 2013 11:05:31 +0000 Message-ID: Subject: Re: [PATCH] Btrfs: fix very slow inode eviction and fs unmount From: Filipe David Manana To: bo.li.liu@oracle.com Cc: "linux-btrfs@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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. > > 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."