[dm-devel] [PATCH] dm-statistics: report precise timestamps and histogram

[Mikulas Patocka]

Mike, please submit this patch to the upstream kernel before 4.2 is 
released, so that the all the kernels that support the options 
"precise_timestamps" and "histogram" also report these values back.


From: Mikulas Patocka <mpatocka at redhat.com>

If the user selected precise timestamps or histogram, report it in the
output of the @stats_list message.

If the user didn't select these options, no extra tokens are reported,
thus it is backward compatible with old software that doesn't know about
precise timestamps and histogram.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

Index: linux-4.1.5/Documentation/device-mapper/statistics.txt
===================================================================
--- linux-4.1.5.orig/Documentation/device-mapper/statistics.txt
+++ linux-4.1.5/Documentation/device-mapper/statistics.txt
@@ -118,6 +118,10 @@ Messages
 
 	Output format:
 	  <region_id>: <start_sector>+<length> <step> <program_id> <aux_data>
+	  	precise_timestamps histogram:n1,n2,n3,...
+
+	The strings "precise_timestamps" and "histogram" are printed only
+	if they were specified when creating the region.
 
     @stats_print <region_id> [<starting_line> <number_of_lines>]
 
Index: linux-4.1.5/drivers/md/dm-stats.c
===================================================================
--- linux-4.1.5.orig/drivers/md/dm-stats.c
+++ linux-4.1.5/drivers/md/dm-stats.c
@@ -453,12 +453,24 @@ static int dm_stats_list(struct dm_stats
 	list_for_each_entry(s, &stats->list, list_entry) {
 		if (!program || !strcmp(program, s->program_id)) {
 			len = s->end - s->start;
-			DMEMIT("%d: %llu+%llu %llu %s %s\n", s->id,
+			DMEMIT("%d: %llu+%llu %llu %s %s", s->id,
 				(unsigned long long)s->start,
 				(unsigned long long)len,
 				(unsigned long long)s->step,
 				s->program_id,
 				s->aux_data);
+			if (s->stat_flags & STAT_PRECISE_TIMESTAMPS)
+				DMEMIT(" precise_timestamps");
+			if (s->n_histogram_entries) {
+				unsigned i;
+				DMEMIT(" histogram:");
+				for (i = 0; i < s->n_histogram_entries; i++) {
+					if (i)
+						DMEMIT(",");
+					DMEMIT("%llu", s->histogram_boundaries[i]);
+				}
+			}
+			DMEMIT("\n");
 		}
 	}
 	mutex_unlock(&stats->mutex);