bcache: finish incremental GC
In GC thread, we record the latest GC key in gc_done, which is expected
to be used for incremental GC, but in currently code, we didn't realize
it. When GC runs, front side IO would be blocked until the GC over, it
would be a long time if there is a lot of btree nodes.
This patch realizes incremental GC, the main ideal is that, when there
are front side I/Os, after GC some nodes (100), we stop GC, release locker
of the btree node, and go to process the front side I/Os for some times
(100 ms), then go back to GC again.
By this patch, when we doing GC, I/Os are not blocked all the time, and
there is no obvious I/Os zero jump problem any more.
Patch v2: Rename some variables and macros name as Coly suggested.
Signed-off-by: Tang Junhui <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 3226d38b..872ef4d 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -474,6 +474,7 @@ struct cache {
struct gc_stat {
size_t nodes;
+ size_t nodes_pre;
size_t key_bytes;
size_t nkeys;
@@ -604,6 +605,10 @@ struct cache_set {
*/
atomic_t rescale;
/*
+ * used for GC, identify if any front side I/Os is inflight
+ */
+ atomic_t search_inflight;
+ /*
* When we invalidate buckets, we use both the priority and the amount
* of good data to determine which buckets to reuse first - to weight
* those together consistently we keep track of the smallest nonzero
