Remove an expensive lock from Timer

The Timer destructor would grab a global mutex in order to update
execution time. Add a class to define a category once, statically; the
class adds itself to an atomic singly linked list, and thus subsequent
updates only need to use an atomic rather than grab a lock and perform a
hashtable lookup.

Differential Revision: https://reviews.llvm.org/D32823
Patch by Scott Smith <scott.smith@purestorage.com>.

llvm-svn: 303058

1 files changed, 12 insertions, 5 deletions

diff --git a/lldb/unittests/Core/TimerTest.cpp b/lldb/unittests/Core/TimerTest.cpp
index 7e7eeef0a36..a35df0d49c8 100644
--- a/lldb/unittests/Core/TimerTest.cpp
+++ b/lldb/unittests/Core/TimerTest.cpp
@@ -18,7 +18,8 @@ using namespace lldb_private;
 TEST(TimerTest, CategoryTimes) {
   Timer::ResetCategoryTimes();
   {
-    Timer t("CAT1", "");
+    static Timer::Category tcat("CAT1");
+    Timer t(tcat, "");
     std::this_thread::sleep_for(std::chrono::milliseconds(10));
   }
   StreamString ss;
@@ -32,14 +33,18 @@ TEST(TimerTest, CategoryTimes) {
 TEST(TimerTest, CategoryTimesNested) {
   Timer::ResetCategoryTimes();
   {
-    Timer t1("CAT1", "");
+    static Timer::Category tcat1("CAT1");
+    Timer t1(tcat1, "");
     std::this_thread::sleep_for(std::chrono::milliseconds(10));
-    Timer t2("CAT1", "");
+    // Explicitly testing the same category as above.
+    Timer t2(tcat1, "");
     std::this_thread::sleep_for(std::chrono::milliseconds(10));
   }
   StreamString ss;
   Timer::DumpCategoryTimes(&ss);
   double seconds;
+  // It should only appear once.
+  ASSERT_EQ(ss.GetString().count("CAT1"), 1U);
   ASSERT_EQ(1, sscanf(ss.GetData(), "%lf sec for CAT1", &seconds));
   EXPECT_LT(0.002, seconds);
   EXPECT_GT(0.2, seconds);
@@ -48,9 +53,11 @@ TEST(TimerTest, CategoryTimesNested) {
 TEST(TimerTest, CategoryTimes2) {
   Timer::ResetCategoryTimes();
   {
-    Timer t1("CAT1", "");
+    static Timer::Category tcat1("CAT1");
+    Timer t1(tcat1, "");
     std::this_thread::sleep_for(std::chrono::milliseconds(100));
-    Timer t2("CAT2", "");
+    static Timer::Category tcat2("CAT2");
+    Timer t2(tcat2, "");
     std::this_thread::sleep_for(std::chrono::milliseconds(10));
   }
   StreamString ss;