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| author | Mikulas Patocka <mpatocka@redhat.com> | 2012-07-27 16:08:02 +0200 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2012-07-27 16:08:02 +0200 |
| commit | 33d07c0dfab902a7c5420587984497dc05ab5c9c (patch) | |
| tree | a81d17ca4633bc43a5fc0959754df43c109a0b63 | |
| parent | dm stripe: remove minimum stripe size (diff) | |
| download | linux-33d07c0dfab902a7c5420587984497dc05ab5c9c.tar.xz linux-33d07c0dfab902a7c5420587984497dc05ab5c9c.zip | |
dm stripe: optimize chunk_size calculations
dm-stripe is usually used with a chunk size that is a power of two.
Use faster shifts and bit masks in such cases.
stripe_width is already optimized in a similar way.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
| -rw-r--r-- | drivers/md/dm-stripe.c | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c index 6a20e9ea0bfb..9e8f4cc63d6c 100644 --- a/drivers/md/dm-stripe.c +++ b/drivers/md/dm-stripe.c @@ -31,6 +31,7 @@ struct stripe_c { sector_t stripe_width; uint32_t chunk_size; + int chunk_size_shift; /* Needed for handling events */ struct dm_target *ti; @@ -163,6 +164,10 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv) ti->num_discard_requests = stripes; sc->chunk_size = chunk_size; + if (chunk_size & (chunk_size - 1)) + sc->chunk_size_shift = -1; + else + sc->chunk_size_shift = __ffs(chunk_size); /* * Get the stripe destinations. @@ -202,7 +207,14 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector, uint32_t *stripe, sector_t *result) { sector_t chunk = dm_target_offset(sc->ti, sector); - sector_t chunk_offset = sector_div(chunk, sc->chunk_size); + sector_t chunk_offset; + + if (sc->chunk_size_shift < 0) + chunk_offset = sector_div(chunk, sc->chunk_size); + else { + chunk_offset = chunk & (sc->chunk_size - 1); + chunk >>= sc->chunk_size_shift; + } if (sc->stripes_shift < 0) *stripe = sector_div(chunk, sc->stripes); @@ -211,7 +223,12 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector, chunk >>= sc->stripes_shift; } - *result = (chunk * sc->chunk_size) + chunk_offset; + if (sc->chunk_size_shift < 0) + chunk *= sc->chunk_size; + else + chunk <<= sc->chunk_size_shift; + + *result = chunk + chunk_offset; } static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector, @@ -225,7 +242,10 @@ static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector, /* round down */ sector = *result; - *result -= sector_div(sector, sc->chunk_size); + if (sc->chunk_size_shift < 0) + *result -= sector_div(sector, sc->chunk_size); + else + *result = sector & ~(sector_t)(sc->chunk_size - 1); if (target_stripe < stripe) *result += sc->chunk_size; /* next chunk */ |