| Message ID | 20220819024408.9714-1-ethanlien@synology.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] btrfs: remove unnecessary EXTENT_UPTODATE state in buffered I/O path | expand |
On Fri, Aug 19, 2022 at 10:44:08AM +0800, ethanlien wrote: > From: Ethan Lien <ethanlien@synology.com> > > After we copied data to page cache in buffered I/O, we > 1. Insert a EXTENT_UPTODATE state into inode's io_tree, by > endio_readpage_release_extent(), set_extent_delalloc() or > set_extent_defrag(). > 2. Set page uptodate before we unlock the page. > > But the only place we check io_tree's EXTENT_UPTODATE state is in > btrfs_do_readpage(). We know we enter btrfs_do_readpage() only when we > have a non-uptodate page, so it is unnecessary to set EXTENT_UPTODATE. > > For example, when performing a buffered random read: > > fio --rw=randread --ioengine=libaio --direct=0 --numjobs=4 \ > --filesize=32G --size=4G --bs=4k --name=job \ > --filename=/mnt/file --name=job > > Then check how many extent_state in io_tree: > > cat /proc/slabinfo | grep btrfs_extent_state | awk '{print $2}' > > w/o this patch, we got 640567 btrfs_extent_state. > w/ this patch, we got 204 btrfs_extent_state. > > Maintaining such a big tree brings overhead since every I/O needs to insert > EXTENT_LOCKED, insert EXTENT_UPTODATE, then remove EXTENT_LOCKED. And in > every insert or remove, we need to lock io_tree, do tree search, alloc or > dealloc extent states. By removing unnecessary EXTENT_UPTODATE, we keep > io_tree in a minimal size and reduce overhead when performing buffered I/O. > > Signed-off-by: Ethan Lien <ethanlien@synology.com> > Reviewed-by: Robbie Ko <robbieko@synology.com> > --- > > V2: Remove set_extent_uptodate() from btrfs_get_extent(), and when we found > a inline extent, set page uptodate in btrfs_do_readpage(). Yep, that was what I had in mind. Thanks for trying it out. I've given it some testing, including a full run of fstests just to confirm I hadn't missed something. Looks good, so: Reviewed-by: Filipe Manana <fdmanana@suse.com> Thanks. > > fs/btrfs/extent-io-tree.h | 4 ++-- > fs/btrfs/extent_io.c | 16 +--------------- > fs/btrfs/inode.c | 2 -- > 3 files changed, 3 insertions(+), 19 deletions(-) > > diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h > index c3eb52dbe61c..53ae849d0248 100644 > --- a/fs/btrfs/extent-io-tree.h > +++ b/fs/btrfs/extent-io-tree.h > @@ -211,7 +211,7 @@ static inline int set_extent_delalloc(struct extent_io_tree *tree, u64 start, > struct extent_state **cached_state) > { > return set_extent_bit(tree, start, end, > - EXTENT_DELALLOC | EXTENT_UPTODATE | extra_bits, > + EXTENT_DELALLOC | extra_bits, > 0, NULL, cached_state, GFP_NOFS, NULL); > } > > @@ -219,7 +219,7 @@ static inline int set_extent_defrag(struct extent_io_tree *tree, u64 start, > u64 end, struct extent_state **cached_state) > { > return set_extent_bit(tree, start, end, > - EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG, > + EXTENT_DELALLOC | EXTENT_DEFRAG, > 0, NULL, cached_state, GFP_NOFS, NULL); > } > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index bfae67c593c5..7e082770a088 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -2924,9 +2924,6 @@ static void endio_readpage_release_extent(struct processed_extent *processed, > * Now we don't have range contiguous to the processed range, release > * the processed range now. > */ > - if (processed->uptodate && tree->track_uptodate) > - set_extent_uptodate(tree, processed->start, processed->end, > - &cached, GFP_ATOMIC); > unlock_extent_cached_atomic(tree, processed->start, processed->end, > &cached); > > @@ -3718,20 +3715,9 @@ static int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, > continue; > } > /* the get_extent function already copied into the page */ > - if (test_range_bit(tree, cur, cur_end, > - EXTENT_UPTODATE, 1, NULL)) { > - unlock_extent(tree, cur, cur + iosize - 1); > - end_page_read(page, true, cur, iosize); > - cur = cur + iosize; > - pg_offset += iosize; > - continue; > - } > - /* we have an inline extent but it didn't get marked up > - * to date. Error out > - */ > if (block_start == EXTENT_MAP_INLINE) { > unlock_extent(tree, cur, cur + iosize - 1); > - end_page_read(page, false, cur, iosize); > + end_page_read(page, true, cur, iosize); > cur = cur + iosize; > pg_offset += iosize; > continue; > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index f0c97d25b4a0..639edbcce9fe 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -7031,8 +7031,6 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode, > } > flush_dcache_page(page); > } > - set_extent_uptodate(io_tree, em->start, > - extent_map_end(em) - 1, NULL, GFP_NOFS); > goto insert; > } > not_found: > -- > 2.17.1 >
On Fri, Aug 19, 2022 at 10:44:08AM +0800, ethanlien wrote: > From: Ethan Lien <ethanlien@synology.com> > > After we copied data to page cache in buffered I/O, we > 1. Insert a EXTENT_UPTODATE state into inode's io_tree, by > endio_readpage_release_extent(), set_extent_delalloc() or > set_extent_defrag(). > 2. Set page uptodate before we unlock the page. > > But the only place we check io_tree's EXTENT_UPTODATE state is in > btrfs_do_readpage(). We know we enter btrfs_do_readpage() only when we > have a non-uptodate page, so it is unnecessary to set EXTENT_UPTODATE. > > For example, when performing a buffered random read: > > fio --rw=randread --ioengine=libaio --direct=0 --numjobs=4 \ > --filesize=32G --size=4G --bs=4k --name=job \ > --filename=/mnt/file --name=job > > Then check how many extent_state in io_tree: > > cat /proc/slabinfo | grep btrfs_extent_state | awk '{print $2}' > > w/o this patch, we got 640567 btrfs_extent_state. > w/ this patch, we got 204 btrfs_extent_state. > > Maintaining such a big tree brings overhead since every I/O needs to insert > EXTENT_LOCKED, insert EXTENT_UPTODATE, then remove EXTENT_LOCKED. And in > every insert or remove, we need to lock io_tree, do tree search, alloc or > dealloc extent states. By removing unnecessary EXTENT_UPTODATE, we keep > io_tree in a minimal size and reduce overhead when performing buffered I/O. > > Signed-off-by: Ethan Lien <ethanlien@synology.com> > Reviewed-by: Robbie Ko <robbieko@synology.com> > --- > > V2: Remove set_extent_uptodate() from btrfs_get_extent(), and when we found > a inline extent, set page uptodate in btrfs_do_readpage(). Added to misc-next, thanks.
diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h index c3eb52dbe61c..53ae849d0248 100644 --- a/fs/btrfs/extent-io-tree.h +++ b/fs/btrfs/extent-io-tree.h @@ -211,7 +211,7 @@ static inline int set_extent_delalloc(struct extent_io_tree *tree, u64 start, struct extent_state **cached_state) { return set_extent_bit(tree, start, end, - EXTENT_DELALLOC | EXTENT_UPTODATE | extra_bits, + EXTENT_DELALLOC | extra_bits, 0, NULL, cached_state, GFP_NOFS, NULL); } @@ -219,7 +219,7 @@ static inline int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end, struct extent_state **cached_state) { return set_extent_bit(tree, start, end, - EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG, + EXTENT_DELALLOC | EXTENT_DEFRAG, 0, NULL, cached_state, GFP_NOFS, NULL); } diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index bfae67c593c5..7e082770a088 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -2924,9 +2924,6 @@ static void endio_readpage_release_extent(struct processed_extent *processed, * Now we don't have range contiguous to the processed range, release * the processed range now. */ - if (processed->uptodate && tree->track_uptodate) - set_extent_uptodate(tree, processed->start, processed->end, - &cached, GFP_ATOMIC); unlock_extent_cached_atomic(tree, processed->start, processed->end, &cached); @@ -3718,20 +3715,9 @@ static int btrfs_do_readpage(struct page *page, struct extent_map **em_cached, continue; } /* the get_extent function already copied into the page */ - if (test_range_bit(tree, cur, cur_end, - EXTENT_UPTODATE, 1, NULL)) { - unlock_extent(tree, cur, cur + iosize - 1); - end_page_read(page, true, cur, iosize); - cur = cur + iosize; - pg_offset += iosize; - continue; - } - /* we have an inline extent but it didn't get marked up - * to date. Error out - */ if (block_start == EXTENT_MAP_INLINE) { unlock_extent(tree, cur, cur + iosize - 1); - end_page_read(page, false, cur, iosize); + end_page_read(page, true, cur, iosize); cur = cur + iosize; pg_offset += iosize; continue; diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index f0c97d25b4a0..639edbcce9fe 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -7031,8 +7031,6 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode, } flush_dcache_page(page); } - set_extent_uptodate(io_tree, em->start, - extent_map_end(em) - 1, NULL, GFP_NOFS); goto insert; } not_found: