Re: [PATCH] cyclictest histogram overflow instance tracking

[Bhavesh Davda <bhavesh@vmware.com>]

Thanks for the review, Frank.

On Oct 11, 2012, at 12:57 PM, Frank Rowand wrote:
> Nice idea…
Thanks

> Suggest:
>        printf("# Histogram Overflows at cycle number:");
> 
Done

>> - 		printf(" %05lu", par[j]->stats->hist_overflow);
>> +		printf(" %05lu", par[j]->stats->hist_overflow);
> 
> Am I blind, or is that a whitespace change?  (The latest version I have does not seem
> to have any white space issues in that line.)
> 
Turns out I had removed extraneous whitespace. My vim settings allow me to see extraneous whitespaces in red, so I get annoyed by them and can fix them up. So I've removed a few more in the revised diffs (sorry!)

> Suggest:
> 
>  +             printf("# thread %d:", j);
> 
Done

> Nit: You don't need stats->outliers_overflow.  You can calculate it from
> stats->hist_overflow - stats->num_outliers:
> 
Nice catch! I've removed outliers_overflow now.


From: Bhavesh Davda <bhavesh@vmware.com>

Add feature to cyclictest histogram mode to track cycle counts every time a
sample overflows the histogram limit. This should help identify if there is a
timing pattern to jitters in cyclictest runs.

Example output (with -h 10):
  ...
  Histogram Overflows: 00000 00253 00000 00005 00000 00024 00003 00005
  Histogram Overflow at cycle number:
  Thread 0:
  Thread 1: 00023 00028 00337 00338 00339 00340 00341 00342 00343 00344 # 00243 others
  Thread 2:
  Thread 3: 10486 10487 10488 10489 10490
  Thread 4:
  Thread 5: 00002 00004 00008 00012 00178 10458 10459 10460 10461 10462 # 00014 others
  Thread 6: 05954 08954 29955
  Thread 7: 20536 20537 20538 20539 20540
  ...

Signed-off-by: Bhavesh Davda <bhavesh@vmware.com>
---
 src/cyclictest/cyclictest.c |   38 +++++++++++++++++++++++++++++---------
 1 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
index 731b4bd..dc985de 100644
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c
@@ -147,6 +147,7 @@ struct thread_stat {
 	double avg;
 	long *values;
 	long *hist_array;
+        unsigned long *outliers;
 	pthread_t thread;
 	int threadstarted;
 	int tid;
@@ -154,6 +155,7 @@ struct thread_stat {
 	long redmax;
 	long cycleofmax;
 	long hist_overflow;
+        long num_outliers;
 };
 
 static int shutdown;
@@ -756,8 +758,11 @@ void *timerthread(void *param)
 
 		/* Update the histogram */
 		if (histogram) {
-			if (diff >= histogram)
+			if (diff >= histogram) {
 				stat->hist_overflow++;
+				if (stat->num_outliers < histogram)
+					stat->outliers[stat->num_outliers++] = stat->cycles - 1;
+			}
 			else
 				stat->hist_array[diff]++;
 		}
@@ -811,7 +816,7 @@ static void display_help(int error)
 		if (kernvar(O_RDONLY, "available_tracers", tracers, sizeof(tracers)))
 			strcpy(tracers, "none");
 	}
-		
+
 	printf("cyclictest V %1.2f\n", VERSION_STRING);
 	printf("Usage:\n"
 	       "cyclictest <options>\n\n"
@@ -1188,7 +1193,7 @@ static int check_kernel(void)
 		kv = KV_30;
 		strcpy(functiontracer, "function");
 		strcpy(traceroptions, "trace_options");
-		
+
 	} else
 		kv = KV_NOT_SUPPORTED;
 
@@ -1226,7 +1231,7 @@ static void print_tids(struct thread_param *par[], int nthreads)
 
 static void print_hist(struct thread_param *par[], int nthreads)
 {
-	int i, j;
+	int i, j, k;
 	unsigned long long int log_entries[nthreads+1];
 	unsigned long maxmax, alloverflows;
 
@@ -1270,7 +1275,7 @@ static void print_hist(struct thread_param *par[], int nthreads)
 	printf("# Max Latencies:");
 	maxmax = 0;
 	for (j = 0; j < nthreads; j++) {
- 		printf(" %05lu", par[j]->stats->max);
+		printf(" %05lu", par[j]->stats->max);
 		if (par[j]->stats->max > maxmax)
 			maxmax = par[j]->stats->max;
 	}
@@ -1280,9 +1285,20 @@ static void print_hist(struct thread_param *par[], int nthreads)
 	printf("# Histogram Overflows:");
 	alloverflows = 0;
 	for (j = 0; j < nthreads; j++) {
- 		printf(" %05lu", par[j]->stats->hist_overflow);
+		printf(" %05lu", par[j]->stats->hist_overflow);
 		alloverflows += par[j]->stats->hist_overflow;
 	}
+	printf("\n");
+	printf("# Histogram Overflow at cycle number:\n");
+	for (j = 0; j < nthreads; j++) {
+		printf("# Thread %d:", j);
+		for (k = 0; k < par[j]->stats->num_outliers; k++)
+			printf(" %05lu", par[j]->stats->outliers[k]);
+		if (par[j]->stats->num_outliers < par[j]->stats->hist_overflow)
+			printf(" # %05lu others", par[j]->stats->hist_overflow - par[j]->stats->num_outliers);
+                printf("\n");
+        }
+
 	if (histofall && nthreads > 1)
 		printf(" %05lu", alloverflows);
 	printf("\n");
@@ -1434,10 +1450,12 @@ int main(int argc, char **argv)
 			int bufsize = histogram * sizeof(long);
 
 			stat->hist_array = threadalloc(bufsize, node);
-			if (stat->hist_array == NULL)
+			stat->outliers = threadalloc(bufsize, node);
+			if (stat->hist_array == NULL || stat->outliers == NULL)
 				fatal("failed to allocate histogram of size %d on node %d\n",
 				      histogram, i);
 			memset(stat->hist_array, 0, bufsize);
+			memset(stat->outliers, 0, bufsize);
 		}
 
 		if (verbose) {
@@ -1553,8 +1571,10 @@ int main(int argc, char **argv)
 
 	if (histogram) {
 		print_hist(parameters, num_threads);
-		for (i = 0; i < num_threads; i++)
+		for (i = 0; i < num_threads; i++) {
 			threadfree(statistics[i]->hist_array, histogram*sizeof(long), parameters[i]->node);
+			threadfree(statistics[i]->outliers, histogram*sizeof(long), parameters[i]->node);
+                }
 	}
 
 	if (tracelimit) {
@@ -1564,7 +1584,7 @@ int main(int argc, char **argv)
 			printf("# Break value: %lu\n", break_thread_value);
 		}
 	}
-	
+
 
 	for (i=0; i < num_threads; i++) {
 		if (!statistics[i])
-- 
1.7.1

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