f2fs: introduce f2fs_issue_flush to avoid redundant flush issue
Some storage devices show relatively high latencies to complete cache_flush
commands, even though their normal IO speed is prettry much high. In such
the case, it needs to merge cache_flush commands as much as possible to avoid
issuing them redundantly.
So, this patch introduces a mount option, "-o flush_merge", to mitigate such
the overhead.
If this option is enabled by user, F2FS merges the cache_flush commands and then
issues just one cache_flush on behalf of them. Once the single command is
finished, F2FS sends a completion signal to all the pending threads.
Note that, this option can be used under a workload consisting of very intensive
concurrent fsync calls, while the storage handles cache_flush commands slowly.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1e3d869..2ecac83 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -40,6 +40,7 @@
#define F2FS_MOUNT_DISABLE_EXT_IDENTIFY 0x00000040
#define F2FS_MOUNT_INLINE_XATTR 0x00000080
#define F2FS_MOUNT_INLINE_DATA 0x00000100
+#define F2FS_MOUNT_FLUSH_MERGE 0x00000200
#define clear_opt(sbi, option) (sbi->mount_opt.opt &= ~F2FS_MOUNT_##option)
#define set_opt(sbi, option) (sbi->mount_opt.opt |= F2FS_MOUNT_##option)
@@ -316,6 +317,12 @@
NO_CHECK_TYPE
};
+struct flush_cmd {
+ struct flush_cmd *next;
+ struct completion wait;
+ int ret;
+};
+
struct f2fs_sm_info {
struct sit_info *sit_info; /* whole segment information */
struct free_segmap_info *free_info; /* free segment information */
@@ -344,6 +351,14 @@
unsigned int ipu_policy; /* in-place-update policy */
unsigned int min_ipu_util; /* in-place-update threshold */
+
+ /* for flush command control */
+ struct task_struct *f2fs_issue_flush; /* flush thread */
+ wait_queue_head_t flush_wait_queue; /* waiting queue for wake-up */
+ struct flush_cmd *issue_list; /* list for command issue */
+ struct flush_cmd *dispatch_list; /* list for command dispatch */
+ spinlock_t issue_lock; /* for issue list lock */
+ struct flush_cmd *issue_tail; /* list tail of issue list */
};
/*
@@ -1160,6 +1175,7 @@
*/
void f2fs_balance_fs(struct f2fs_sb_info *);
void f2fs_balance_fs_bg(struct f2fs_sb_info *);
+int f2fs_issue_flush(struct f2fs_sb_info *);
void invalidate_blocks(struct f2fs_sb_info *, block_t);
void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
void clear_prefree_segments(struct f2fs_sb_info *);