[RFCv5 5/5] iomap: Add per-block dirty state tracking to improve performance

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



When filesystem blocksize is less than folio size (either with
mapping_large_folio_support() or with blocksize < pagesize) and when the
folio is uptodate in pagecache, then even a byte write can cause
an entire folio to be written to disk during writeback. This happens
because we currently don't have a mechanism to track per-block dirty
state within struct iomap_page. We currently only track uptodate state.

This patch implements support for tracking per-block dirty state in
iomap_page->state bitmap. This should help improve the filesystem write
performance and help reduce write amplification.

Performance testing of below fio workload reveals ~16x performance
improvement using nvme with XFS (4k blocksize) on Power (64K pagesize)
FIO reported write bw scores improved from around ~28 MBps to ~452 MBps.

1. <test_randwrite.fio>
[global]
	ioengine=psync
	rw=randwrite
	overwrite=1
	pre_read=1
	direct=0
	bs=4k
	size=1G
	dir=./
	numjobs=8
	fdatasync=1
	runtime=60
	iodepth=64
	group_reporting=1

[fio-run]

2. Also our internal performance team reported that this patch improves
   their database workload performance by around ~83% (with XFS on Power)

Reported-by: Aravinda Herle <araherle@xxxxxxxxxx>
Reported-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
---
 fs/gfs2/aops.c         |   2 +-
 fs/iomap/buffered-io.c | 115 ++++++++++++++++++++++++++++++++++++++---
 fs/xfs/xfs_aops.c      |   2 +-
 fs/zonefs/file.c       |   2 +-
 include/linux/iomap.h  |   1 +
 5 files changed, 112 insertions(+), 10 deletions(-)

diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index a5f4be6b9213..75efec3c3b71 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -746,7 +746,7 @@ static const struct address_space_operations gfs2_aops = {
 	.writepages = gfs2_writepages,
 	.read_folio = gfs2_read_folio,
 	.readahead = gfs2_readahead,
-	.dirty_folio = filemap_dirty_folio,
+	.dirty_folio = iomap_dirty_folio,
 	.release_folio = iomap_release_folio,
 	.invalidate_folio = iomap_invalidate_folio,
 	.bmap = gfs2_bmap,
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 25f20f269214..c7f41b26280a 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -52,6 +52,12 @@ static inline void iop_set_range(struct iomap_page *iop, unsigned int start_blk,
 	bitmap_set(iop->state, start_blk, nr_blks);
 }

+static inline void iop_clear_range(struct iomap_page *iop,
+				   unsigned int start_blk, unsigned int nr_blks)
+{
+	bitmap_clear(iop->state, start_blk, nr_blks);
+}
+
 static inline bool iop_test_block(struct iomap_page *iop, unsigned int block)
 {
 	return test_bit(block, iop->state);
@@ -84,6 +90,16 @@ static bool iop_test_block_uptodate(struct folio *folio, unsigned int block)
 	return iop_test_block(iop, block);
 }

+static bool iop_test_block_dirty(struct folio *folio, int block)
+{
+	struct iomap_page *iop = to_iomap_page(folio);
+	struct inode *inode = folio->mapping->host;
+	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
+
+	WARN_ON(!iop);
+	return iop_test_block(iop, block + blks_per_folio);
+}
+
 static void iop_set_range_uptodate(struct inode *inode, struct folio *folio,
 				   size_t off, size_t len)
 {
@@ -104,8 +120,42 @@ static void iop_set_range_uptodate(struct inode *inode, struct folio *folio,
 	}
 }

+static void iop_set_range_dirty(struct inode *inode, struct folio *folio,
+				size_t off, size_t len)
+{
+	struct iomap_page *iop = to_iomap_page(folio);
+	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
+	unsigned int first_blk = (off >> inode->i_blkbits);
+	unsigned int last_blk = ((off + len - 1) >> inode->i_blkbits);
+	unsigned int nr_blks = last_blk - first_blk + 1;
+	unsigned long flags;
+
+	if (!iop)
+		return;
+	spin_lock_irqsave(&iop->state_lock, flags);
+	iop_set_range(iop, first_blk + blks_per_folio, nr_blks);
+	spin_unlock_irqrestore(&iop->state_lock, flags);
+}
+
+static void iop_clear_range_dirty(struct folio *folio, size_t off, size_t len)
+{
+	struct iomap_page *iop = to_iomap_page(folio);
+	struct inode *inode = folio->mapping->host;
+	unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
+	unsigned int first_blk = (off >> inode->i_blkbits);
+	unsigned int last_blk = ((off + len - 1) >> inode->i_blkbits);
+	unsigned int nr_blks = last_blk - first_blk + 1;
+	unsigned long flags;
+
+	if (!iop)
+		return;
+	spin_lock_irqsave(&iop->state_lock, flags);
+	iop_clear_range(iop, first_blk + blks_per_folio, nr_blks);
+	spin_unlock_irqrestore(&iop->state_lock, flags);
+}
+
 static struct iomap_page *iop_alloc(struct inode *inode, struct folio *folio,
-				    unsigned int flags)
+				    unsigned int flags, bool is_dirty)
 {
 	struct iomap_page *iop = to_iomap_page(folio);
 	unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
@@ -119,12 +169,20 @@ static struct iomap_page *iop_alloc(struct inode *inode, struct folio *folio,
 	else
 		gfp = GFP_NOFS | __GFP_NOFAIL;

-	iop = kzalloc(struct_size(iop, state, BITS_TO_LONGS(nr_blocks)),
+	/*
+	 * iop->state tracks two sets of state flags when the
+	 * filesystem block size is smaller than the folio size.
+	 * The first state tracks per-block uptodate and the
+	 * second tracks per-block dirty state.
+	 */
+	iop = kzalloc(struct_size(iop, state, BITS_TO_LONGS(2 * nr_blocks)),
 		      gfp);
 	if (iop) {
 		spin_lock_init(&iop->state_lock);
 		if (folio_test_uptodate(folio))
 			iop_set_range(iop, 0, nr_blocks);
+		if (is_dirty)
+			iop_set_range(iop, nr_blocks, nr_blocks);
 		folio_attach_private(folio, iop);
 	}
 	return iop;
@@ -268,7 +326,8 @@ static int iomap_read_inline_data(const struct iomap_iter *iter,
 	if (WARN_ON_ONCE(size > iomap->length))
 		return -EIO;
 	if (offset > 0)
-		iop = iop_alloc(iter->inode, folio, iter->flags);
+		iop = iop_alloc(iter->inode, folio, iter->flags,
+				folio_test_dirty(folio));
 	else
 		iop = to_iomap_page(folio);

@@ -306,7 +365,8 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 		return iomap_read_inline_data(iter, folio);

 	/* zero post-eof blocks as the page may be mapped */
-	iop = iop_alloc(iter->inode, folio, iter->flags);
+	iop = iop_alloc(iter->inode, folio, iter->flags,
+			folio_test_dirty(folio));
 	iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
 	if (plen == 0)
 		goto done;
@@ -561,6 +621,18 @@ void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len)
 }
 EXPORT_SYMBOL_GPL(iomap_invalidate_folio);

+bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio)
+{
+	struct iomap_page *iop;
+	struct inode *inode = mapping->host;
+	size_t len = i_blocks_per_folio(inode, folio) << inode->i_blkbits;
+
+	iop = iop_alloc(inode, folio, 0, false);
+	iop_set_range_dirty(inode, folio, 0, len);
+	return filemap_dirty_folio(mapping, folio);
+}
+EXPORT_SYMBOL_GPL(iomap_dirty_folio);
+
 static void
 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
 {
@@ -608,7 +680,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 	    pos + len >= folio_pos(folio) + folio_size(folio))
 		return 0;

-	iop = iop_alloc(iter->inode, folio, iter->flags);
+	iop = iop_alloc(iter->inode, folio, iter->flags,
+			folio_test_dirty(folio));

 	if ((iter->flags & IOMAP_NOWAIT) && !iop && nr_blocks > 1)
 		return -EAGAIN;
@@ -767,6 +840,7 @@ static size_t __iomap_write_end(struct inode *inode, loff_t pos, size_t len,
 	if (unlikely(copied < len && !folio_test_uptodate(folio)))
 		return 0;
 	iop_set_range_uptodate(inode, folio, offset_in_folio(folio, pos), len);
+	iop_set_range_dirty(inode, folio, offset_in_folio(folio, pos), copied);
 	filemap_dirty_folio(inode->i_mapping, folio);
 	return copied;
 }
@@ -954,6 +1028,10 @@ static int iomap_write_delalloc_scan(struct inode *inode,
 {
 	while (start_byte < end_byte) {
 		struct folio	*folio;
+		struct iomap_page *iop;
+		unsigned int first_blk, last_blk, blks_per_folio, i;
+		loff_t last_byte;
+		u8 blkbits = inode->i_blkbits;

 		/* grab locked page */
 		folio = filemap_lock_folio(inode->i_mapping,
@@ -978,6 +1056,28 @@ static int iomap_write_delalloc_scan(struct inode *inode,
 				}
 			}

+			/*
+			 * When we have per-block dirty tracking, there can be
+			 * blocks within a folio which are marked uptodate
+			 * but not dirty. In that case it is necessary to punch
+			 * out such blocks to avoid leaking any delalloc blocks.
+			 */
+			iop = to_iomap_page(folio);
+			if (!iop)
+				goto skip_iop_punch;
+			last_byte = min_t(loff_t, end_byte - 1,
+				(folio_next_index(folio) << PAGE_SHIFT) - 1);
+			first_blk = offset_in_folio(folio, start_byte) >>
+						    blkbits;
+			last_blk = offset_in_folio(folio, last_byte) >>
+						   blkbits;
+			blks_per_folio = i_blocks_per_folio(inode, folio);
+			for (i = first_blk; i <= last_blk; i++) {
+				if (!iop_test_block_dirty(folio, i))
+					punch(inode, i << blkbits,
+						     1 << blkbits);
+			}
+skip_iop_punch:
 			/*
 			 * Make sure the next punch start is correctly bound to
 			 * the end of this data range, not the end of the folio.
@@ -1666,7 +1766,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
 		struct writeback_control *wbc, struct inode *inode,
 		struct folio *folio, u64 end_pos)
 {
-	struct iomap_page *iop = iop_alloc(inode, folio, 0);
+	struct iomap_page *iop = iop_alloc(inode, folio, 0, true);
 	struct iomap_ioend *ioend, *next;
 	unsigned len = i_blocksize(inode);
 	unsigned nblocks = i_blocks_per_folio(inode, folio);
@@ -1682,7 +1782,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
 	 * invalid, grab a new one.
 	 */
 	for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
-		if (iop && !iop_test_block_uptodate(folio, i))
+		if (iop && !iop_test_block_dirty(folio, i))
 			continue;

 		error = wpc->ops->map_blocks(wpc, inode, pos);
@@ -1726,6 +1826,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
 		}
 	}

+	iop_clear_range_dirty(folio, 0, end_pos - folio_pos(folio));
 	folio_start_writeback(folio);
 	folio_unlock(folio);

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 2ef78aa1d3f6..77c7332ae197 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -578,7 +578,7 @@ const struct address_space_operations xfs_address_space_operations = {
 	.read_folio		= xfs_vm_read_folio,
 	.readahead		= xfs_vm_readahead,
 	.writepages		= xfs_vm_writepages,
-	.dirty_folio		= filemap_dirty_folio,
+	.dirty_folio		= iomap_dirty_folio,
 	.release_folio		= iomap_release_folio,
 	.invalidate_folio	= iomap_invalidate_folio,
 	.bmap			= xfs_vm_bmap,
diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
index 132f01d3461f..e508c8e97372 100644
--- a/fs/zonefs/file.c
+++ b/fs/zonefs/file.c
@@ -175,7 +175,7 @@ const struct address_space_operations zonefs_file_aops = {
 	.read_folio		= zonefs_read_folio,
 	.readahead		= zonefs_readahead,
 	.writepages		= zonefs_writepages,
-	.dirty_folio		= filemap_dirty_folio,
+	.dirty_folio		= iomap_dirty_folio,
 	.release_folio		= iomap_release_folio,
 	.invalidate_folio	= iomap_invalidate_folio,
 	.migrate_folio		= filemap_migrate_folio,
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 0f8123504e5e..0c2bee80565c 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -264,6 +264,7 @@ bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
 struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos);
 bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
 void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
+bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio);
 int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 		const struct iomap_ops *ops);
 int iomap_zero_range(struct inode *inode, loff_t pos, loff_t len,
--
2.39.2




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux