On Tue, Apr 17, 2018 at 04:19:04PM -0700, Howard McLauchlan wrote:
> Presently, convert_free_space_to_extents() does a linear scan of the
> bitmap. We can speed this up with find_next_{bit,zero_bit}_le().
>
> This patch replaces the linear scan with find_next_{bit,zero_bit}_le().
> Testing shows a 20-33% decrease in execution time for
> convert_free_space_to_extents().
Sounds good.
> Suggested-by: Omar Sandoval <osandov@xxxxxxxxxxx>
> Signed-off-by: Howard McLauchlan <hmclauchlan@xxxxxx>
> ---
> Based on 4.17-rc1
>
> fs/btrfs/extent_io.c | 12 ++++-----
> fs/btrfs/extent_io.h | 4 +--
> fs/btrfs/free-space-tree.c | 54 ++++++++++++++------------------------
> 3 files changed, 27 insertions(+), 43 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index e99b329002cf..1c0e7ce49556 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -5620,12 +5620,12 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
> }
> }
>
> -void le_bitmap_set(u8 *map, unsigned int start, int len)
> +void le_bitmap_set(unsigned long *map, unsigned int start, int len)
> {
> - u8 *p = map + BIT_BYTE(start);
> + char *p = ((char *)map) + BIT_BYTE(start);
> const unsigned int size = start + len;
> int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
> - u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
> + char mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
Why do you switch to char? As there are bit operations done below (that
you don't change), the unsigned type seems correct.
>
> while (len - bits_to_set >= 0) {
> *p |= mask_to_set;
> @@ -5640,12 +5640,12 @@ void le_bitmap_set(u8 *map, unsigned int start, int len)
> }
> }
>
> -void le_bitmap_clear(u8 *map, unsigned int start, int len)
> +void le_bitmap_clear(unsigned long *map, unsigned int start, int len)
> {
> - u8 *p = map + BIT_BYTE(start);
> + char *p = ((char *)map) + BIT_BYTE(start);
> const unsigned int size = start + len;
> int bits_to_clear = BITS_PER_BYTE - (start % BITS_PER_BYTE);
> - u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(start);
> + char mask_to_clear = BITMAP_FIRST_BYTE_MASK(start);
Same here and in below. Otherwise it looks ok.
>
> while (len - bits_to_clear >= 0) {
> *p &= ~mask_to_clear;
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index a53009694b16..a6db233f4a40 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -84,8 +84,8 @@ static inline int le_test_bit(int nr, const u8 *addr)
> return 1U & (addr[BIT_BYTE(nr)] >> (nr & (BITS_PER_BYTE-1)));
> }
>
> -void le_bitmap_set(u8 *map, unsigned int start, int len);
> -void le_bitmap_clear(u8 *map, unsigned int start, int len);
> +void le_bitmap_set(unsigned long *map, unsigned int start, int len);
> +void le_bitmap_clear(unsigned long *map, unsigned int start, int len);
>
> struct extent_state;
> struct btrfs_root;
> diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
> index 32a0f6cb5594..0ddf96b01a3a 100644
> --- a/fs/btrfs/free-space-tree.c
> +++ b/fs/btrfs/free-space-tree.c
> @@ -138,9 +138,9 @@ static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
> return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
> }
>
> -static u8 *alloc_bitmap(u32 bitmap_size)
> +static unsigned long *alloc_bitmap(u32 bitmap_size)
> {
> - u8 *ret;
> + unsigned long *ret;
> unsigned int nofs_flag;
>
> /*
> @@ -166,7 +166,8 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
> struct btrfs_free_space_info *info;
> struct btrfs_key key, found_key;
> struct extent_buffer *leaf;
> - u8 *bitmap, *bitmap_cursor;
> + unsigned long *bitmap;
> + char *bitmap_cursor;
> u64 start, end;
> u64 bitmap_range, i;
> u32 bitmap_size, flags, expected_extent_count;
> @@ -255,7 +256,7 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
> goto out;
> }
>
> - bitmap_cursor = bitmap;
> + bitmap_cursor = (char *)bitmap;
> bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
> i = start;
> while (i < end) {
> @@ -304,13 +305,10 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
> struct btrfs_free_space_info *info;
> struct btrfs_key key, found_key;
> struct extent_buffer *leaf;
> - u8 *bitmap;
> + unsigned long *bitmap;
> u64 start, end;
> - /* Initialize to silence GCC. */
> - u64 extent_start = 0;
> - u64 offset;
> u32 bitmap_size, flags, expected_extent_count;
> - int prev_bit = 0, bit, bitnr;
> + unsigned long nrbits, start_bit, end_bit;
> u32 extent_count = 0;
> int done = 0, nr;
> int ret;
> @@ -348,7 +346,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
> break;
> } else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
> unsigned long ptr;
> - u8 *bitmap_cursor;
> + char *bitmap_cursor;
> u32 bitmap_pos, data_size;
>
> ASSERT(found_key.objectid >= start);
> @@ -358,7 +356,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
> bitmap_pos = div_u64(found_key.objectid - start,
> fs_info->sectorsize *
> BITS_PER_BYTE);
> - bitmap_cursor = bitmap + bitmap_pos;
> + bitmap_cursor = ((char *)bitmap) + bitmap_pos;
> data_size = free_space_bitmap_size(found_key.offset,
> fs_info->sectorsize);
>
> @@ -392,32 +390,16 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
> btrfs_mark_buffer_dirty(leaf);
> btrfs_release_path(path);
>
> - offset = start;
> - bitnr = 0;
> - while (offset < end) {
> - bit = !!le_test_bit(bitnr, bitmap);
> - if (prev_bit == 0 && bit == 1) {
> - extent_start = offset;
> - } else if (prev_bit == 1 && bit == 0) {
> - key.objectid = extent_start;
> - key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
> - key.offset = offset - extent_start;
> -
> - ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
> - if (ret)
> - goto out;
> - btrfs_release_path(path);
> + nrbits = div_u64(block_group->key.offset, block_group->fs_info->sectorsize);
> + start_bit = find_next_bit_le(bitmap, nrbits, 0);
>
> - extent_count++;
> - }
> - prev_bit = bit;
> - offset += fs_info->sectorsize;
> - bitnr++;
> - }
> - if (prev_bit == 1) {
> - key.objectid = extent_start;
> + while (start_bit < nrbits) {
> + end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
> + ASSERT(start_bit < end_bit);
> +
> + key.objectid = start + start_bit * block_group->fs_info->sectorsize;
> key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
> - key.offset = end - extent_start;
> + key.offset = (end_bit - start_bit) * block_group->fs_info->sectorsize;
>
> ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
> if (ret)
> @@ -425,6 +407,8 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
> btrfs_release_path(path);
>
> extent_count++;
> +
> + start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
> }
>
> if (extent_count != expected_extent_count) {
> --
> 2.17.0
>
> --
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