On Mon, Dec 16, 2013 at 11:45 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> 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 <bo.li.liu@xxxxxxxxxx> 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.
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 <fdmanana@xxxxxxxxx>
>> >> ---
>> >> 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
>> >>
>> >> --
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>> >> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> >> 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."
--
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