bcache: Incremental gc
Big garbage collection rewrite; now, garbage collection uses the same
mechanisms as used elsewhere for inserting/updating btree node pointers,
instead of rewriting interior btree nodes in place.
This makes the code significantly cleaner and less fragile, and means we
can now make garbage collection incremental - it doesn't have to hold a
write lock on the root of the btree for the entire duration of garbage
collection.
This means that there's less of a latency hit for doing garbage
collection, which means we can gc more frequently (and do a better job
of reclaiming from the cache), and we can coalesce across more btree
nodes (improving our space efficiency).
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h
index e11bb85..b5a46af 100644
--- a/drivers/md/bcache/btree.h
+++ b/drivers/md/bcache/btree.h
@@ -201,7 +201,7 @@
static inline void set_gc_sectors(struct cache_set *c)
{
- atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 8);
+ atomic_set(&c->sectors_to_gc, c->sb.bucket_size * c->nbuckets / 16);
}
static inline struct bkey *bch_btree_iter_init(struct btree *b,