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>
diff --git a/block/blk-core.c b/block/blk-core.c
index 4c090a0..b2e5764 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3583,76 +3583,43 @@
* TODO : If necessary, we can make the histograms per-cpu and aggregate
* them when printing them out.
*/
-void
-blk_zero_latency_hist(struct io_latency_state *s)
-{
- memset(s->latency_y_axis_read, 0,
- sizeof(s->latency_y_axis_read));
- memset(s->latency_y_axis_write, 0,
- sizeof(s->latency_y_axis_write));
- s->latency_reads_elems = 0;
- s->latency_writes_elems = 0;
-}
-EXPORT_SYMBOL(blk_zero_latency_hist);
-
ssize_t
-blk_latency_hist_show(struct io_latency_state *s, char *buf)
+blk_latency_hist_show(char* name, struct io_latency_state *s, char *buf,
+ int buf_size)
{
int i;
int bytes_written = 0;
u_int64_t num_elem, elem;
int pct;
+ u_int64_t average;
- num_elem = s->latency_reads_elems;
- if (num_elem > 0) {
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "IO svc_time Read Latency Histogram (n = %llu):\n",
- num_elem);
- for (i = 0;
- i < ARRAY_SIZE(latency_x_axis_us);
- i++) {
- elem = s->latency_y_axis_read[i];
- pct = div64_u64(elem * 100, num_elem);
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "\t< %5lluus%15llu%15d%%\n",
- latency_x_axis_us[i],
- elem, pct);
- }
- /* Last element in y-axis table is overflow */
- elem = s->latency_y_axis_read[i];
- pct = div64_u64(elem * 100, num_elem);
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "\t> %5dms%15llu%15d%%\n", 10,
- elem, pct);
+ num_elem = s->latency_elems;
+ if (num_elem > 0) {
+ average = div64_u64(s->latency_sum, s->latency_elems);
+ bytes_written += scnprintf(buf + bytes_written,
+ buf_size - bytes_written,
+ "IO svc_time %s Latency Histogram (n = %llu,"
+ " average = %llu):\n", name, num_elem, average);
+ for (i = 0;
+ i < ARRAY_SIZE(latency_x_axis_us);
+ i++) {
+ elem = s->latency_y_axis[i];
+ pct = div64_u64(elem * 100, num_elem);
+ bytes_written += scnprintf(buf + bytes_written,
+ PAGE_SIZE - bytes_written,
+ "\t< %6lluus%15llu%15d%%\n",
+ latency_x_axis_us[i],
+ elem, pct);
+ }
+ /* Last element in y-axis table is overflow */
+ elem = s->latency_y_axis[i];
+ pct = div64_u64(elem * 100, num_elem);
+ bytes_written += scnprintf(buf + bytes_written,
+ PAGE_SIZE - bytes_written,
+ "\t>=%6lluus%15llu%15d%%\n",
+ latency_x_axis_us[i - 1], elem, pct);
}
- num_elem = s->latency_writes_elems;
- if (num_elem > 0) {
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "IO svc_time Write Latency Histogram (n = %llu):\n",
- num_elem);
- for (i = 0;
- i < ARRAY_SIZE(latency_x_axis_us);
- i++) {
- elem = s->latency_y_axis_write[i];
- pct = div64_u64(elem * 100, num_elem);
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "\t< %5lluus%15llu%15d%%\n",
- latency_x_axis_us[i],
- elem, pct);
- }
- /* Last element in y-axis table is overflow */
- elem = s->latency_y_axis_write[i];
- pct = div64_u64(elem * 100, num_elem);
- bytes_written += scnprintf(buf + bytes_written,
- PAGE_SIZE - bytes_written,
- "\t> %5dms%15llu%15d%%\n", 10,
- elem, pct);
- }
+
return bytes_written;
}
EXPORT_SYMBOL(blk_latency_hist_show);