diff options
Diffstat (limited to 'drivers/md/dm-snap-persistent.c')
| -rw-r--r-- | drivers/md/dm-snap-persistent.c | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c index 169275050c0b..afc3d017de4c 100644 --- a/drivers/md/dm-snap-persistent.c +++ b/drivers/md/dm-snap-persistent.c @@ -18,6 +18,8 @@ #define DM_MSG_PREFIX "persistent snapshot" #define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */ +#define DM_PREFETCH_CHUNKS 12 + /*----------------------------------------------------------------- * Persistent snapshots, by persistent we mean that the snapshot * will survive a reboot. @@ -497,6 +499,7 @@ static int read_exceptions(struct pstore *ps, { int r, full = 1; struct dm_bufio_client *client; + chunk_t prefetch_area = 0; client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev, ps->store->chunk_size << SECTOR_SHIFT, @@ -506,13 +509,33 @@ static int read_exceptions(struct pstore *ps, return PTR_ERR(client); /* + * Setup for one current buffer + desired readahead buffers. + */ + dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS); + + /* * Keeping reading chunks and inserting exceptions until * we find a partially full area. */ for (ps->current_area = 0; full; ps->current_area++) { struct dm_buffer *bp; void *area; - chunk_t chunk = area_location(ps, ps->current_area); + chunk_t chunk; + + if (unlikely(prefetch_area < ps->current_area)) + prefetch_area = ps->current_area; + + if (DM_PREFETCH_CHUNKS) do { + chunk_t pf_chunk = area_location(ps, prefetch_area); + if (unlikely(pf_chunk >= dm_bufio_get_device_size(client))) + break; + dm_bufio_prefetch(client, pf_chunk, 1); + prefetch_area++; + if (unlikely(!prefetch_area)) + break; + } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS); + + chunk = area_location(ps, ps->current_area); area = dm_bufio_read(client, chunk, &bp); if (unlikely(IS_ERR(area))) { |