4 files changed, 32 insertions, 4 deletions
diff --git a/src/Makefile.bench.include b/src/Makefile.bench.include
index 126e3a102f..61fe9e287d 100644
--- a/src/Makefile.bench.include
+++ b/src/Makefile.bench.include
@@ -7,7 +7,7 @@ bench_bench_bitcoin_SOURCES = \
   bench/bench_bitcoin.cpp \
   bench/bench.cpp \
   bench/bench.h \
-  bench/MilliSleep.cpp
+  bench/Examples.cpp
 
 bench_bench_bitcoin_CPPFLAGS = $(BITCOIN_INCLUDES) $(EVENT_CLFAGS) $(EVENT_PTHREADS_CFLAGS) -I$(builddir)/bench/
 bench_bench_bitcoin_LDADD = \
diff --git a/src/bench/MilliSleep.cpp b/src/bench/Examples.cpp
index 991397a234..b6b020a971 100644
--- a/src/bench/MilliSleep.cpp
+++ b/src/bench/Examples.cpp
@@ -6,6 +6,8 @@
 #include "main.h"
 #include "utiltime.h"
 
+// Sanity test: this should loop ten times, and
+// min/max/average should be close to 100ms.
 static void Sleep100ms(benchmark::State& state)
 {
     while (state.KeepRunning()) {
@@ -14,3 +16,19 @@ static void Sleep100ms(benchmark::State& state)
 }
 
 BENCHMARK(Sleep100ms);
+
+// Extremely fast-running benchmark:
+#include <math.h>
+
+volatile double sum = 0.0; // volatile, global so not optimized away
+
+static void Trig(benchmark::State& state)
+{
+    double d = 0.01;
+    while (state.KeepRunning()) {
+        sum += sin(d);
+        d += 0.000001;
+    }
+}
+
+BENCHMARK(Trig);
diff --git a/src/bench/bench.cpp b/src/bench/bench.cpp
index 5720807609..89c3b0cc2a 100644
--- a/src/bench/bench.cpp
+++ b/src/bench/bench.cpp
@@ -36,14 +36,22 @@ BenchRunner::RunAll(double elapsedTimeForOne)
 
 bool State::KeepRunning()
 {
-    double now = gettimedouble();
+    double now;
     if (count == 0) {
-        beginTime = now;
+        beginTime = now = gettimedouble();
     }
     else {
-        double elapsedOne = now - lastTime;
+        // timeCheckCount is used to avoid calling gettime most of the time,
+        // so benchmarks that run very quickly get consistent results.
+        if ((count+1)%timeCheckCount != 0) {
+            ++count;
+            return true; // keep going
+        }
+        now = gettimedouble();
+        double elapsedOne = (now - lastTime)/timeCheckCount;
         if (elapsedOne < minTime) minTime = elapsedOne;
         if (elapsedOne > maxTime) maxTime = elapsedOne;
+        if (elapsedOne*timeCheckCount < maxElapsed/16) timeCheckCount *= 2;
     }
     lastTime = now;
     ++count;
diff --git a/src/bench/bench.h b/src/bench/bench.h
index fee9b8c38d..bf591a2be6 100644
--- a/src/bench/bench.h
+++ b/src/bench/bench.h
@@ -41,10 +41,12 @@ namespace benchmark {
         double beginTime;
         double lastTime, minTime, maxTime;
         int64_t count;
+        int64_t timeCheckCount;
     public:
         State(std::string _name, double _maxElapsed) : name(_name), maxElapsed(_maxElapsed), count(0) {
             minTime = std::numeric_limits<double>::max();
             maxTime = std::numeric_limits<double>::min();
+            timeCheckCount = 1;
         }
         bool KeepRunning();
     };