From 36ff72b10ca0e9b12abae12eb83c24f2d10d8e67 Mon Sep 17 00:00:00 2001
From: nixon <nixon@fb.com>
Date: Wed, 15 Aug 2012 15:02:46 -0700
Subject: [PATCH] Added variance calculation of histogram latency reporting.
---
.../measurements/OneMeasurementHistogram.java | 47 ++++++++++++++++---
1 file changed, 41 insertions(+), 6 deletions(-)
diff --git a/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHistogram.java b/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHistogram.java
index 2cba955a..4e8f5642 100644
--- a/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHistogram.java
+++ b/core/src/main/java/com/yahoo/ycsb/measurements/OneMeasurementHistogram.java
@@ -36,11 +36,39 @@ public class OneMeasurementHistogram extends OneMeasurement
public static final String BUCKETS="histogram.buckets";
public static final String BUCKETS_DEFAULT="1000";
+
+ /**
+ * Specify the range of latencies to track in the histogram.
+ */
int _buckets;
+
+ /**
+ * Groups operations in discrete blocks of 1ms width.
+ */
int[] histogram;
+
+ /**
+ * Counts all operations outside the histogram's range.
+ */
int histogramoverflow;
+
+ /**
+ * The total number of reported operations.
+ */
int operations;
- long totallatency;
+
+ /**
+ * The sum of each latency measurement over all operations.
+ * Calculated in ms.
+ */
+ double totallatency;
+
+ /**
+ * The sum of each latency measurement squared over all operations.
+ * Used to calculate variance of latency.
+ * Calculated in ms.
+ */
+ double totalsquaredlatency;
//keep a windowed version of these stats for printing status
int windowoperations;
@@ -58,6 +86,7 @@ public class OneMeasurementHistogram extends OneMeasurement
histogramoverflow=0;
operations=0;
totallatency=0;
+ totalsquaredlatency=0;
windowoperations=0;
windowtotallatency=0;
min=-1;
@@ -86,6 +115,7 @@ public class OneMeasurementHistogram extends OneMeasurement
*/
public synchronized void measure(int latency)
{
+ //latency reported in us and collected in bucket by ms.
if (latency/1000>=_buckets)
{
histogramoverflow++;
@@ -95,10 +125,11 @@ public class OneMeasurementHistogram extends OneMeasurement
histogram[latency/1000]++;
}
operations++;
- totallatency+=latency;
+ totallatency += ((double)latency) / 1000;
+ totalsquaredlatency += ((double)latency) * ((double)latency) / 1000000;
windowoperations++;
- windowtotallatency+=latency;
-
+ windowtotallatency += latency;
+
if ( (min<0) || (latency<min) )
{
min=latency;
@@ -112,10 +143,14 @@ public class OneMeasurementHistogram extends OneMeasurement
@Override
- public void exportMeasurements(MeasurementsExporter exporter) throws IOException
+ public void exportMeasurements(MeasurementsExporter exporter)
+ throws IOException
{
+ double mean = totallatency/((double)operations);
+ double variance = totalsquaredlatency/((double)operations) - (mean * mean);
exporter.write(getName(), "Operations", operations);
- exporter.write(getName(), "AverageLatency(us)", (((double)totallatency)/((double)operations)));
+ exporter.write(getName(), "AverageLatency(ms)", mean);
+ exporter.write(getName(), "LatencyVariance(ms)", variance);
exporter.write(getName(), "MinLatency(us)", min);
exporter.write(getName(), "MaxLatency(us)", max);
--
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