drbd: use rolling marks for resync speed calculation

The current resync speed as displayed in /proc/drbd fluctuates a lot.
Using an array of rolling marks makes this calculation much more stable.
We used to have this (a long time ago with 0.7), but it got lost somehow.

If "stalled", do not discard the rest of the information, just add a
" (stalled)" tag to the progress line.

This patch also shortens a spinlock critical section somewhat, and
reduces the number of atomic operations in put_ldev.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 17 insertions, 10 deletions

diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index be3374b68460..c159692c3b56 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -57,6 +57,7 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	unsigned long db, dt, dbdt, rt, rs_left;
 	unsigned int res;
 	int i, x, y;
+	int stalled = 0;
 
 	drbd_get_syncer_progress(mdev, &rs_left, &res);
 
@@ -90,18 +91,17 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	 * db: blocks written from mark until now
 	 * rt: remaining time
 	 */
-	dt = (jiffies - mdev->rs_mark_time) / HZ;
-
-	if (dt > 20) {
-		/* if we made no update to rs_mark_time for too long,
-		 * we are stalled. show that. */
-		seq_printf(seq, "stalled\n");
-		return;
-	}
+	/* Rolling marks. last_mark+1 may just now be modified.  last_mark+2 is
+	 * at least (DRBD_SYNC_MARKS-2)*DRBD_SYNC_MARK_STEP old, and has at
+	 * least DRBD_SYNC_MARK_STEP time before it will be modified. */
+	i = (mdev->rs_last_mark + 2) % DRBD_SYNC_MARKS;
+	dt = (jiffies - mdev->rs_mark_time[i]) / HZ;
+	if (dt > (DRBD_SYNC_MARK_STEP * DRBD_SYNC_MARKS))
+		stalled = 1;
 
 	if (!dt)
 		dt++;
-	db = mdev->rs_mark_left - rs_left;
+	db = mdev->rs_mark_left[i] - rs_left;
 	rt = (dt * (rs_left / (db/100+1)))/100; /* seconds */
 
 	seq_printf(seq, "finish: %lu:%02lu:%02lu",
@@ -128,7 +128,14 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	else
 		seq_printf(seq, " (%ld)", dbdt);
 
-	seq_printf(seq, " K/sec\n");
+	if (mdev->state.conn == C_SYNC_TARGET) {
+		if (mdev->c_sync_rate > 1000)
+			seq_printf(seq, " want: %d,%03d",
+				   mdev->c_sync_rate / 1000, mdev->c_sync_rate % 1000);
+		else
+			seq_printf(seq, " want: %d", mdev->c_sync_rate);
+	}
+	seq_printf(seq, " K/sec%s\n", stalled ? " (stalled)" : "");
 }
 
 static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)