diff options
| author |   Mikulas Patocka <mpatocka@redhat.com> | 2010-08-12 04:14:21 +0100 |
|---|---|---|
| committer |   Alasdair G Kergon <agk@redhat.com> | 2010-08-12 04:14:21 +0100 |
| commit | c96053b767d494d7c30e2be68097ac9defa9403f (patch) | |
| tree | b66f185ffd58538f6107f3acf3af38b8aecd7f8a /drivers/md | |
| parent | dm stripe: move sector translation to a function (diff) | |
| download | linux-dev-c96053b767d494d7c30e2be68097ac9defa9403f.tar.xz linux-dev-c96053b767d494d7c30e2be68097ac9defa9403f.zip | |
dm stripe: optimize sector division
Optimize sector division: If the number of stripes is a power of two,
we can do shift and mask instead of division.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-stripe.c | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c index e2ad1ae5268d..1559fdfd2073 100644 --- a/drivers/md/dm-stripe.c +++ b/drivers/md/dm-stripe.c @@ -25,6 +25,8 @@ struct stripe { struct stripe_c { uint32_t stripes; + int stripes_shift; + sector_t stripes_mask; /* The size of this target / num. stripes */ sector_t stripe_width; @@ -162,16 +164,21 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv) /* Set pointer to dm target; used in trigger_event */ sc->ti = ti; - sc->stripes = stripes; sc->stripe_width = width; + + if (stripes & (stripes - 1)) + sc->stripes_shift = -1; + else { + sc->stripes_shift = ffs(stripes) - 1; + sc->stripes_mask = ((sector_t) stripes) - 1; + } + ti->split_io = chunk_size; ti->num_flush_requests = stripes; + sc->chunk_shift = ffs(chunk_size) - 1; sc->chunk_mask = ((sector_t) chunk_size) - 1; - for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++) - chunk_size >>= 1; - sc->chunk_shift--; /* * Get the stripe destinations. @@ -213,7 +220,13 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector, sector_t offset = dm_target_offset(sc->ti, sector); sector_t chunk = offset >> sc->chunk_shift; - *stripe = sector_div(chunk, sc->stripes); + if (sc->stripes_shift < 0) + *stripe = sector_div(chunk, sc->stripes); + else { + *stripe = chunk & sc->stripes_mask; + chunk >>= sc->stripes_shift; + } + *result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask); } |