From: Mingzhe Zou <zoumingzhe@xxxxxx>
Moving gc uses cache->heap to defragment disk. Unlike btree gc,
moving gc only takes up part of the disk bandwidth.
The number of heap is constant. However, the buckets released by
each moving gc is limited. So bch_moving_gc() needs to be called
multiple times.
If bch_gc_thread() always calls bch_btree_gc(), it will block
the IO request.This patch allows bch_gc_thread() to only call
bch_moving_gc() when there are many fragments.
Signed-off-by: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>
---
drivers/md/bcache/bcache.h | 4 +-
drivers/md/bcache/btree.c | 73 ++++++++++++++++++++++++++++++++++--
drivers/md/bcache/movinggc.c | 7 +++-
drivers/md/bcache/super.c | 2 +
4 files changed, 81 insertions(+), 5 deletions(-)
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 582df3c9dc1b..10f3f548629e 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -459,7 +459,8 @@ struct cache {
* until a gc finishes - otherwise we could pointlessly burn a ton of
* cpu
*/
- unsigned int invalidate_needs_gc;
+ unsigned int invalidate_needs_gc:1;
+ unsigned int only_moving_gc:1;
bool discard; /* Get rid of? */
@@ -627,6 +628,7 @@ struct cache_set {
struct gc_stat gc_stats;
size_t nbuckets;
size_t avail_nbuckets;
+ size_t fragment_nbuckets;
struct task_struct *gc_thread;
/* Where in the btree gc currently is */
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index ca962f329977..baa2149e9235 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -88,6 +88,7 @@
* Test module load/unload
*/
+#define COPY_GC_PERCENT 5
#define MAX_NEED_GC 64
#define MAX_SAVE_PRIO 72
#define MAX_GC_TIMES 100
@@ -1726,6 +1727,7 @@ static void btree_gc_start(struct cache_set *c)
mutex_lock(&c->bucket_lock);
+ set_gc_sectors(c);
c->gc_mark_valid = 0;
c->gc_done = ZERO_KEY;
@@ -1852,8 +1854,58 @@ static void bch_btree_gc(struct cache_set *c)
memcpy(&c->gc_stats, &stats, sizeof(struct gc_stat));
trace_bcache_gc_end(c);
+}
+
+extern unsigned int bch_cutoff_writeback;
+extern unsigned int bch_cutoff_writeback_sync;
+
+static bool moving_gc_should_run(struct cache_set *c)
+{
+ struct bucket *b;
+ struct cache *ca = c->cache;
+ size_t moving_gc_threshold = ca->sb.bucket_size >> 2, frag_percent;
+ unsigned long used_buckets = 0, frag_buckets = 0, move_buckets = 0;
+ unsigned long dirty_sectors = 0, frag_sectors = 0, used_sectors = 0;
+
+ mutex_lock(&c->bucket_lock);
+ for_each_bucket(b, ca) {
+ if (GC_MOVE(b) || GC_MARK(b) != GC_MARK_DIRTY)
+ continue;
+
+ used_buckets++;
+
+ used_sectors = b->gc_sectors_used;
+ dirty_sectors += used_sectors;
+
+ if (used_sectors < ca->sb.bucket_size)
+ frag_buckets++;
+
+ if (used_sectors <= moving_gc_threshold)
+ move_buckets++;
+ }
+ mutex_unlock(&c->bucket_lock);
+
+ c->fragment_nbuckets = frag_buckets;
- bch_moving_gc(c);
+ if (used_buckets < c->nbuckets * bch_cutoff_writeback / 100)
+ return false;
+
+ if (move_buckets > ca->heap.size)
+ return true;
+
+ frag_sectors = used_buckets * ca->sb.bucket_size - dirty_sectors;
+ frag_percent = div_u64(frag_sectors * 100, ca->sb.bucket_size * c->nbuckets);
+
+ if (frag_percent >= COPY_GC_PERCENT)
+ return true;
+
+ if (used_buckets > c->nbuckets * bch_cutoff_writeback_sync / 100)
+ return true;
+
+ if (c->gc_stats.in_use > bch_cutoff_writeback_sync && frag_buckets > 0)
+ return true;
+
+ return false;
}
static bool gc_should_run(struct cache_set *c)
@@ -1866,6 +1918,19 @@ static bool gc_should_run(struct cache_set *c)
if (atomic_read(&c->sectors_to_gc) < 0)
return true;
+ /*
+ * Moving gc uses cache->heap to defragment disk. Unlike btree gc,
+ * moving gc only takes up part of the disk bandwidth.
+ * The number of heap is constant. However, the buckets released by
+ * each moving gc is limited. So bch_moving_gc() needs to be called
+ * multiple times. If bch_gc_thread() always calls bch_btree_gc(),
+ * it will block the IO request.
+ */
+ if (c->copy_gc_enabled && moving_gc_should_run(c)) {
+ ca->only_moving_gc = 1;
+ return true;
+ }
+
return false;
}
@@ -1883,8 +1948,10 @@ static int bch_gc_thread(void *arg)
test_bit(CACHE_SET_IO_DISABLE, &c->flags))
break;
- set_gc_sectors(c);
- bch_btree_gc(c);
+ if (!c->cache->only_moving_gc)
+ bch_btree_gc(c);
+
+ bch_moving_gc(c);
}
wait_for_kthread_stop();
diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c
index e4182c3ba9f8..7c01e1565191 100644
--- a/drivers/md/bcache/movinggc.c
+++ b/drivers/md/bcache/movinggc.c
@@ -200,6 +200,8 @@ void bch_moving_gc(struct cache_set *c)
struct bucket *b;
unsigned long sectors_to_move, reserve_sectors;
+ c->cache->only_moving_gc = 0;
+
if (!c->copy_gc_enabled)
return;
@@ -212,7 +214,7 @@ void bch_moving_gc(struct cache_set *c)
ca->heap.used = 0;
for_each_bucket(b, ca) {
- if (GC_MARK(b) == GC_MARK_METADATA ||
+ if (GC_MOVE(b) || GC_MARK(b) == GC_MARK_METADATA ||
!b->gc_sectors_used ||
b->gc_sectors_used == ca->sb.bucket_size ||
atomic_read(&b->pin))
@@ -229,6 +231,9 @@ void bch_moving_gc(struct cache_set *c)
heap_sift(&ca->heap, 0, bucket_cmp);
}
}
+
+ pr_info("moving gc: on set %pU, %lu sectors from %zu buckets",
+ c->sb.set_uuid, sectors_to_move, ca->heap.used);
while (sectors_to_move > reserve_sectors) {
heap_pop(&ca->heap, b, bucket_cmp);
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 0ae2b3676293..7e556bc0ec04 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2112,6 +2112,8 @@ static int run_cache_set(struct cache_set *c)
if (bch_gc_thread_start(c))
goto err;
+ force_wake_up_gc(c);
+
closure_sync(&cl);
c->cache->sb.last_mount = (u32)ktime_get_real_seconds();
bcache_write_super(c);
--
2.17.1.windows.2
