On Sat, Jul 01, 2023 at 01:04:41PM +0530, Ritesh Harjani (IBM) wrote:
> 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_folio_state. We currently only track uptodate
> state.
>
> This patch implements support for tracking per-block dirty state in
> iomap_folio_state->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 | 149 ++++++++++++++++++++++++++++++++++++++---
> fs/xfs/xfs_aops.c | 2 +-
> fs/zonefs/file.c | 2 +-
> include/linux/iomap.h | 1 +
> 5 files changed, 142 insertions(+), 14 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 fb6c2b6a4358..2fd9413838de 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -25,7 +25,7 @@
>
> typedef int (*iomap_punch_t)(struct inode *inode, loff_t offset, loff_t length);
> /*
> - * Structure allocated for each folio to track per-block uptodate state
> + * Structure allocated for each folio to track per-block uptodate, dirty state
> * and I/O completions.
> */
> struct iomap_folio_state {
> @@ -78,6 +78,61 @@ static void iomap_set_range_uptodate(struct folio *folio, size_t off,
> folio_mark_uptodate(folio);
> }
>
> +static inline bool ifs_block_is_dirty(struct folio *folio,
> + struct iomap_folio_state *ifs, int block)
> +{
> + struct inode *inode = folio->mapping->host;
> + unsigned int blks_per_folio = i_blocks_per_folio(inode, folio);
> +
> + return test_bit(block + blks_per_folio, ifs->state);
> +}
> +
> +static void ifs_clear_range_dirty(struct folio *folio,
> + struct iomap_folio_state *ifs, size_t off, size_t len)
> +{
> + 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;
> +
> + spin_lock_irqsave(&ifs->state_lock, flags);
> + bitmap_clear(ifs->state, first_blk + blks_per_folio, nr_blks);
Much clearer now that these have been simplified.
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> + spin_unlock_irqrestore(&ifs->state_lock, flags);
> +}
> +
> +static void iomap_clear_range_dirty(struct folio *folio, size_t off, size_t len)
> +{
> + struct iomap_folio_state *ifs = folio->private;
> +
> + if (ifs)
> + ifs_clear_range_dirty(folio, ifs, off, len);
> +}
> +
> +static void ifs_set_range_dirty(struct folio *folio,
> + struct iomap_folio_state *ifs, size_t off, size_t len)
> +{
> + 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;
> +
> + spin_lock_irqsave(&ifs->state_lock, flags);
> + bitmap_set(ifs->state, first_blk + blks_per_folio, nr_blks);
> + spin_unlock_irqrestore(&ifs->state_lock, flags);
> +}
> +
> +static void iomap_set_range_dirty(struct folio *folio, size_t off, size_t len)
> +{
> + struct iomap_folio_state *ifs = folio->private;
> +
> + if (ifs)
> + ifs_set_range_dirty(folio, ifs, off, len);
> +}
> +
> static struct iomap_folio_state *ifs_alloc(struct inode *inode,
> struct folio *folio, unsigned int flags)
> {
> @@ -93,14 +148,24 @@ static struct iomap_folio_state *ifs_alloc(struct inode *inode,
> else
> gfp = GFP_NOFS | __GFP_NOFAIL;
>
> - ifs = kzalloc(struct_size(ifs, state, BITS_TO_LONGS(nr_blocks)),
> - gfp);
> - if (ifs) {
> - spin_lock_init(&ifs->state_lock);
> - if (folio_test_uptodate(folio))
> - bitmap_fill(ifs->state, nr_blocks);
> - folio_attach_private(folio, ifs);
> - }
> + /*
> + * ifs->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.
> + */
> + ifs = kzalloc(struct_size(ifs, state,
> + BITS_TO_LONGS(2 * nr_blocks)), gfp);
> + if (!ifs)
> + return ifs;
> +
> + spin_lock_init(&ifs->state_lock);
> + if (folio_test_uptodate(folio))
> + bitmap_set(ifs->state, 0, nr_blocks);
> + if (folio_test_dirty(folio))
> + bitmap_set(ifs->state, nr_blocks, nr_blocks);
> + folio_attach_private(folio, ifs);
> +
> return ifs;
> }
>
> @@ -523,6 +588,17 @@ 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 inode *inode = mapping->host;
> + size_t len = folio_size(folio);
> +
> + ifs_alloc(inode, folio, 0);
> + iomap_set_range_dirty(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)
> {
> @@ -727,6 +803,7 @@ 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;
> iomap_set_range_uptodate(folio, offset_in_folio(folio, pos), len);
> + iomap_set_range_dirty(folio, offset_in_folio(folio, pos), copied);
> filemap_dirty_folio(inode->i_mapping, folio);
> return copied;
> }
> @@ -891,6 +968,43 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
> }
> EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
>
> +static int iomap_write_delalloc_ifs_punch(struct inode *inode,
> + struct folio *folio, loff_t start_byte, loff_t end_byte,
> + iomap_punch_t punch)
> +{
> + unsigned int first_blk, last_blk, i;
> + loff_t last_byte;
> + u8 blkbits = inode->i_blkbits;
> + struct iomap_folio_state *ifs;
> + int ret = 0;
> +
> + /*
> + * 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.
> + */
> + ifs = folio->private;
> + if (!ifs)
> + return ret;
> +
> + last_byte = min_t(loff_t, end_byte - 1,
> + folio_pos(folio) + folio_size(folio) - 1);
> + first_blk = offset_in_folio(folio, start_byte) >> blkbits;
> + last_blk = offset_in_folio(folio, last_byte) >> blkbits;
> + for (i = first_blk; i <= last_blk; i++) {
> + if (!ifs_block_is_dirty(folio, ifs, i)) {
> + ret = punch(inode, folio_pos(folio) + (i << blkbits),
> + 1 << blkbits);
> + if (ret)
> + return ret;
> + }
> + }
> +
> + return ret;
> +}
> +
> +
> static int iomap_write_delalloc_punch(struct inode *inode, struct folio *folio,
> loff_t *punch_start_byte, loff_t start_byte, loff_t end_byte,
> iomap_punch_t punch)
> @@ -907,6 +1021,13 @@ static int iomap_write_delalloc_punch(struct inode *inode, struct folio *folio,
> if (ret)
> return ret;
> }
> +
> + /* Punch non-dirty blocks within folio */
> + ret = iomap_write_delalloc_ifs_punch(inode, folio, start_byte,
> + end_byte, punch);
> + if (ret)
> + return ret;
> +
> /*
> * Make sure the next punch start is correctly bound to
> * the end of this data range, not the end of the folio.
> @@ -1637,7 +1758,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> struct writeback_control *wbc, struct inode *inode,
> struct folio *folio, u64 end_pos)
> {
> - struct iomap_folio_state *ifs = ifs_alloc(inode, folio, 0);
> + struct iomap_folio_state *ifs = folio->private;
> struct iomap_ioend *ioend, *next;
> unsigned len = i_blocksize(inode);
> unsigned nblocks = i_blocks_per_folio(inode, folio);
> @@ -1645,6 +1766,11 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> int error = 0, count = 0, i;
> LIST_HEAD(submit_list);
>
> + if (!ifs && nblocks > 1) {
> + ifs = ifs_alloc(inode, folio, 0);
> + iomap_set_range_dirty(folio, 0, folio_size(folio));
> + }
> +
> WARN_ON_ONCE(ifs && atomic_read(&ifs->write_bytes_pending) != 0);
>
> /*
> @@ -1653,7 +1779,7 @@ 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 (ifs && !ifs_block_is_uptodate(ifs, i))
> + if (ifs && !ifs_block_is_dirty(folio, ifs, i))
> continue;
>
> error = wpc->ops->map_blocks(wpc, inode, pos);
> @@ -1697,6 +1823,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> }
> }
>
> + iomap_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 451942fb38ec..2fca4b4e7fd8 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 e2b836c2e119..eb9335c46bf3 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,
> --
> 2.40.1
>
