blkdev: Refactoring block io latency histogram codes

The current io_latency_state structure includes entries for read
and write requests. There are special types of write commands
such as sync and discard (trim) commands, and the current
implementation is not general enough if we want to separate
latency histogram for such special commands.

This change makes io_latency_state structure request-type neutral.
It also changes to print the latency average.

Signed-off-by: Hyojun Kim <hyojun@google.com>

2 files changed, 13 insertions, 29 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index a9562bb029d0..fb5302d6c931 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1694,43 +1694,26 @@ static const u_int64_t latency_x_axis_us[] = {
 #define BLK_IO_LAT_HIST_ZERO            2
 
 struct io_latency_state {
-	u_int64_t	latency_y_axis_read[ARRAY_SIZE(latency_x_axis_us) + 1];
-	u_int64_t	latency_reads_elems;
-	u_int64_t	latency_y_axis_write[ARRAY_SIZE(latency_x_axis_us) + 1];
-	u_int64_t	latency_writes_elems;
+	u_int64_t	latency_y_axis[ARRAY_SIZE(latency_x_axis_us) + 1];
+	u_int64_t	latency_elems;
+	u_int64_t	latency_sum;
 };
 
 static inline void
-blk_update_latency_hist(struct io_latency_state *s,
-			int read,
-			u_int64_t delta_us)
+blk_update_latency_hist(struct io_latency_state *s, u_int64_t delta_us)
 {
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(latency_x_axis_us); i++) {
-		if (delta_us < (u_int64_t)latency_x_axis_us[i]) {
-			if (read)
-				s->latency_y_axis_read[i]++;
-			else
-				s->latency_y_axis_write[i]++;
+	for (i = 0; i < ARRAY_SIZE(latency_x_axis_us); i++)
+		if (delta_us < (u_int64_t)latency_x_axis_us[i])
 			break;
-		}
-	}
-	if (i == ARRAY_SIZE(latency_x_axis_us)) {
-		/* Overflowed the histogram */
-		if (read)
-			s->latency_y_axis_read[i]++;
-		else
-			s->latency_y_axis_write[i]++;
-	}
-	if (read)
-		s->latency_reads_elems++;
-	else
-		s->latency_writes_elems++;
+	s->latency_y_axis[i]++;
+	s->latency_elems++;
+	s->latency_sum += delta_us;
 }
 
-void blk_zero_latency_hist(struct io_latency_state *s);
-ssize_t blk_latency_hist_show(struct io_latency_state *s, char *buf);
+ssize_t blk_latency_hist_show(char* name, struct io_latency_state *s,
+		char *buf, int buf_size);
 
 #else /* CONFIG_BLOCK */
 
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 97b2b0b1f99d..46e91d4fce7e 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -382,7 +382,8 @@ struct mmc_host {
 
 #ifdef CONFIG_BLOCK
 	int			latency_hist_enabled;
-	struct io_latency_state io_lat_s;
+	struct io_latency_state io_lat_read;
+	struct io_latency_state io_lat_write;
 #endif
 
 	unsigned long		private[0] ____cacheline_aligned;