monobench: usability tweaks

 - Allow an second argument to limit the number of samples.
 - If no benchmarks match, warn and exit instead of infinitely looping.

The default limit of 2147483647 10ms samples will run for 9 months, which I think is long enough to not need any special infinity logic.
BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2747

Change-Id: Id70cf77b624e19dc04e1d75a71385aee3c988a80
Reviewed-on: https://skia-review.googlesource.com/2747
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 10 insertions, 4 deletions

diff --git a/tools/monobench.cpp b/tools/monobench.cpp
index 88a6cce37c..756e24f101 100644
--- a/tools/monobench.cpp
+++ b/tools/monobench.cpp
@@ -12,6 +12,7 @@
 #include <chrono>
 #include <regex>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string>
 #include <vector>
 
@@ -23,9 +24,9 @@ int main(int argc, char** argv) {
     using ns = std::chrono::duration<double, std::nano>;
 
     std::regex pattern;
-    if (argc > 1) {
-        pattern = argv[1];
-    }
+    int limit = 2147483647;
+    if (argc > 1) { pattern = argv[1]; }
+    if (argc > 2) { limit = atoi(argv[2]); }
 
     struct Bench {
         std::unique_ptr<Benchmark> b;
@@ -45,6 +46,11 @@ int main(int argc, char** argv) {
         }
     }
 
+    if (benches.size() == 0) {
+        printf("No bench matched.\n");
+        return 1;
+    }
+
     if (benches.size() > 1) {
         int common_prefix = benches[0].name.size();
         for (size_t i = 1; i < benches.size(); i++) {
@@ -78,7 +84,7 @@ int main(int argc, char** argv) {
     }
 
     int samples = 0;
-    for (;;) {
+    while (samples < limit) {
         for (auto& bench : benches) {
             for (int loops = 1; loops < 1000000000;) {
                 bench.b->preDraw(nullptr);