diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2012-07-27 15:08:03 +0100 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-07-27 15:08:03 +0100 |
| commit | f9a8e0cd261fc05820539b0ea613686a32795406 (patch) | |
| tree | 0edf941f787dd10dd674111cfefbde5004348ef4 /drivers/md/dm-thin.c | |
| parent | 4929630901100fdbfa19186ecf5ea2706f57719b (diff) | |
dm thin: optimize power of two block size
dm-thin will be most likely used with a block size that is a power of
two. So it should be optimized for this case.
This patch changes division and modulo operations to shifts and bit
masks if block size is a power of two.
A test that bi_sector is divisible by a block size is removed from
io_overlaps_block. Device mapper never sends bios that span a block
boundary. Consequently, if we tested that bi_size is equivalent to block
size, bi_sector must already be on a block boundary.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-thin.c')
| -rw-r--r-- | drivers/md/dm-thin.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 828649256902..93e3e542cff9 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -512,6 +512,7 @@ struct pool { dm_block_t low_water_blocks; uint32_t sectors_per_block; + int sectors_per_block_shift; struct pool_features pf; unsigned low_water_triggered:1; /* A dm event has been sent */ @@ -679,7 +680,10 @@ static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio) { sector_t block_nr = bio->bi_sector; - (void) sector_div(block_nr, tc->pool->sectors_per_block); + if (tc->pool->sectors_per_block_shift < 0) + (void) sector_div(block_nr, tc->pool->sectors_per_block); + else + block_nr >>= tc->pool->sectors_per_block_shift; return block_nr; } @@ -690,8 +694,12 @@ static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block) sector_t bi_sector = bio->bi_sector; bio->bi_bdev = tc->pool_dev->bdev; - bio->bi_sector = (block * pool->sectors_per_block) + - sector_div(bi_sector, pool->sectors_per_block); + if (tc->pool->sectors_per_block_shift < 0) + bio->bi_sector = (block * pool->sectors_per_block) + + sector_div(bi_sector, pool->sectors_per_block); + else + bio->bi_sector = (block << pool->sectors_per_block_shift) | + (bi_sector & (pool->sectors_per_block - 1)); } static void remap_to_origin(struct thin_c *tc, struct bio *bio) @@ -936,10 +944,7 @@ static void process_prepared(struct pool *pool, struct list_head *head, */ static int io_overlaps_block(struct pool *pool, struct bio *bio) { - sector_t bi_sector = bio->bi_sector; - - return !sector_div(bi_sector, pool->sectors_per_block) && - (bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT)); + return bio->bi_size == (pool->sectors_per_block << SECTOR_SHIFT); } static int io_overwrites_block(struct pool *pool, struct bio *bio) @@ -1721,6 +1726,10 @@ static struct pool *pool_create(struct mapped_device *pool_md, pool->pmd = pmd; pool->sectors_per_block = block_size; + if (block_size & (block_size - 1)) + pool->sectors_per_block_shift = -1; + else + pool->sectors_per_block_shift = __ffs(block_size); pool->low_water_blocks = 0; pool_features_init(&pool->pf); pool->prison = prison_create(PRISON_CELLS); |