dm thin: prefetch missing metadata pages
Prefetch metadata at the start of the worker thread and then again every
128th bio processed from the deferred list.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index eecfe74..97a7eb4 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1526,6 +1526,7 @@
struct bio *bio;
struct bio_list bios;
struct blk_plug plug;
+ unsigned count = 0;
if (tc->requeue_mode) {
requeue_bio_list(tc, &tc->deferred_bio_list);
@@ -1567,6 +1568,10 @@
pool->process_discard(tc, bio);
else
pool->process_bio(tc, bio);
+
+ if ((count++ & 127) == 0) {
+ dm_pool_issue_prefetches(pool->pmd);
+ }
}
blk_finish_plug(&plug);
}
@@ -1652,6 +1657,7 @@
{
struct pool *pool = container_of(ws, struct pool, worker);
+ dm_pool_issue_prefetches(pool->pmd);
process_prepared(pool, &pool->prepared_mappings, &pool->process_prepared_mapping);
process_prepared(pool, &pool->prepared_discards, &pool->process_prepared_discard);
process_deferred_bios(pool);
@@ -1996,10 +2002,6 @@
/* fall through */
case -EWOULDBLOCK:
- /*
- * In future, the failed dm_thin_find_block above could
- * provide the hint to load the metadata into cache.
- */
thin_defer_bio(tc, bio);
cell_defer_no_holder_no_free(tc, &cell1);
return DM_MAPIO_SUBMITTED;