[PATCH 2/2] f2fs: add support for counting the average time of submit discard cmd

[Yangtao Li]

This patch adds support for counting the average time of submit discard
command, and we can see its value in debugfs.

Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
---
 fs/f2fs/debug.c   |  7 +++++--
 fs/f2fs/f2fs.h    |  5 +++++
 fs/f2fs/segment.c | 18 ++++++++++++++++--
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 733b1bd37404..eed3edfc5faf 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -109,6 +109,9 @@ static void update_general_status(struct f2fs_sb_info *sbi)
 			llist_empty(&SM_I(sbi)->fcc_info->issue_list);
 	}
 	if (SM_I(sbi)->dcc_info) {
+		struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+
+		si->discard_avg = dcc->discard_time_avg;
 		si->nr_discarded =
 			atomic_read(&SM_I(sbi)->dcc_info->issued_discard);
 		si->nr_discarding =
@@ -510,8 +513,8 @@ static int stat_show(struct seq_file *s, void *v)
 			   si->nr_wb_cp_data, si->nr_wb_data,
 			   si->nr_flushing, si->nr_flushed,
 			   si->flush_list_empty);
-		seq_printf(s, "Discard: (%4d %4d)) cmd: %4d undiscard:%4u\n",
-			   si->nr_discarding, si->nr_discarded,
+		seq_printf(s, "Discard: (%4d %4d, avg:%4lldns)) cmd: %4d undiscard:%4u\n",
+			   si->nr_discarding, si->nr_discarded, ktime_to_us(si->discard_avg),
 			   si->nr_discard_cmd, si->undiscard_blks);
 		seq_printf(s, "  - atomic IO: %4d (Max. %4d)\n",
 			   si->aw_cnt, si->max_aw_cnt);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index eb8c27c4e5fc..5a99759d10ac 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -370,6 +370,8 @@ struct discard_cmd {
 	int error;			/* bio error */
 	spinlock_t lock;		/* for state/bio_ref updating */
 	unsigned short bio_ref;		/* bio reference count */
+	struct discard_cmd_control *dcc; /* global discard cmd control */
+	ktime_t submit_start;		/* submit start time */
 };
 
 enum {
@@ -414,6 +416,8 @@ struct discard_cmd_control {
 	unsigned int max_ordered_discard;	/* maximum discard granularity issued by lba order */
 	unsigned int undiscard_blks;		/* # of undiscard blocks */
 	unsigned int next_pos;			/* next discard position */
+	spinlock_t discard_time_lock;	/* for discard time statistics */
+	ktime_t discard_time_avg;		/* issued discard cmd avg time */
 	atomic_t issued_discard;		/* # of issued discard */
 	atomic_t queued_discard;		/* # of queued discard */
 	atomic_t discard_cmd_cnt;		/* # of cached cmd count */
@@ -3882,6 +3886,7 @@ struct f2fs_stat_info {
 	int nr_dio_read, nr_dio_write;
 	unsigned int io_skip_bggc, other_skip_bggc;
 	int nr_flushing, nr_flushed, flush_list_empty;
+	ktime_t	discard_avg;
 	int nr_discarding, nr_discarded;
 	int nr_discard_cmd;
 	unsigned int undiscard_blks;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 9486ca49ecb1..bc96b1afb308 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -931,6 +931,7 @@ static struct discard_cmd *__create_discard_cmd(struct f2fs_sb_info *sbi,
 	list_add_tail(&dc->list, pend_list);
 	spin_lock_init(&dc->lock);
 	dc->bio_ref = 0;
+	dc->dcc = dcc;
 	atomic_inc(&dcc->discard_cmd_cnt);
 	dcc->undiscard_blks += len;
 
@@ -1000,9 +1001,13 @@ static void __remove_discard_cmd(struct f2fs_sb_info *sbi,
 static void f2fs_submit_discard_endio(struct bio *bio)
 {
 	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
+	struct discard_cmd_control *dcc = dc->dcc;
 	unsigned long flags;
+	ktime_t submit_time;
+	int nr_discarded;
 
 	spin_lock_irqsave(&dc->lock, flags);
+	submit_time = ktime_sub(ktime_get(), dc->submit_start);
 	if (!dc->error)
 		dc->error = blk_status_to_errno(bio->bi_status);
 	dc->bio_ref--;
@@ -1012,6 +1017,14 @@ static void f2fs_submit_discard_endio(struct bio *bio)
 	}
 	spin_unlock_irqrestore(&dc->lock, flags);
 	bio_put(bio);
+
+	spin_lock_irqsave(&dcc->discard_time_lock, flags);
+	nr_discarded = atomic_read(&dcc->issued_discard);
+	dcc->discard_time_avg = div_u64(ktime_add(nr_discarded * dcc->discard_time_avg,
+										submit_time),
+									nr_discarded + 1);
+	atomic_inc(&dcc->issued_discard);
+	spin_unlock_irqrestore(&dcc->discard_time_lock, flags);
 }
 
 static void __check_sit_bitmap(struct f2fs_sb_info *sbi,
@@ -1160,6 +1173,7 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
 		 * right away
 		 */
 		spin_lock_irqsave(&dc->lock, flags);
+		dc->submit_start = ktime_get();
 		if (last)
 			dc->state = D_SUBMIT;
 		else
@@ -1179,8 +1193,6 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
 		bio->bi_opf |= flag;
 		submit_bio(bio);
 
-		atomic_inc(&dcc->issued_discard);
-
 		f2fs_update_iostat(sbi, NULL, FS_DISCARD, 1);
 
 		lstart += len;
@@ -2070,9 +2082,11 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi)
 	INIT_LIST_HEAD(&dcc->wait_list);
 	INIT_LIST_HEAD(&dcc->fstrim_list);
 	mutex_init(&dcc->cmd_lock);
+	spin_lock_init(&dcc->discard_time_lock);
 	atomic_set(&dcc->issued_discard, 0);
 	atomic_set(&dcc->queued_discard, 0);
 	atomic_set(&dcc->discard_cmd_cnt, 0);
+	dcc->discard_time_avg = 0;
 	dcc->nr_discards = 0;
 	dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg;
 	dcc->max_discard_request = DEF_MAX_DISCARD_REQUEST;
-- 
2.25.1