f2fs: let fstrim issue discard commands in lower priority
The fstrim gathers huge number of large discard commands, and tries to issue
without IO awareness, which results in long user-perceive IO latencies on
READ, WRITE, and FLUSH in UFS. We've observed some of commands take several
seconds due to long discard latency.
This patch limits the maximum size to 2MB per candidate, and check IO congestion
when issuing them to disk.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 84be1e7..dbab522 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -184,6 +184,7 @@
(BATCHED_TRIM_SEGMENTS(sbi) << (sbi)->log_blocks_per_seg)
#define MAX_DISCARD_BLOCKS(sbi) BLKS_PER_SEC(sbi)
#define DEF_MAX_DISCARD_REQUEST 8 /* issue 8 discards per round */
+#define DEF_MAX_DISCARD_LEN 512 /* Max. 2MB per discard */
#define DEF_MIN_DISCARD_ISSUE_TIME 50 /* 50 ms, if exists */
#define DEF_MAX_DISCARD_ISSUE_TIME 60000 /* 60 s, if no candidates */
#define DEF_CP_INTERVAL 60 /* 60 secs */
@@ -692,7 +693,8 @@
static inline bool __is_discard_mergeable(struct discard_info *back,
struct discard_info *front)
{
- return back->lstart + back->len == front->lstart;
+ return (back->lstart + back->len == front->lstart) &&
+ (back->len + front->len < DEF_MAX_DISCARD_LEN);
}
static inline bool __is_discard_back_mergeable(struct discard_info *cur,