Bug 1472668 - Don't reset performance counters when reading their values - r=baku

We're changing the counters behavior since they are not notifications anymore.
In the new behavior they don't get reset when they are retrieved,
so we can have several consumers via the promise.

If the values overflow, we let the wrapping occur (unsigned values).

MozReview-Commit-ID: 1adkszScYo4

--HG--
extra : rebase_source : cd554ad4cfa643b09f75bb07e38b5d35e08cf470

dom/base/DocGroup.cpp

@@ -129,8 +129,6 @@ DocGroup::ReportPerformanceInfo()
     }
   }
 
-  // setting back all counters to zero
-  mPerformanceCounter->ResetPerformanceCounters();
   return PerformanceInfo(host, pid, pwid, duration, false, isTopLevel, items);
 }
 

dom/tests/browser/browser_test_performance_metrics.js

@@ -40,20 +40,16 @@ function postMessageToWorker(tab, message) {
 }
 
 add_task(async function test() {
-  SpecialPowers.setBoolPref('dom.performance.enable_scheduler_timing', true);
+  SpecialPowers.setBoolPref("dom.performance.enable_scheduler_timing", true);
   waitForExplicitFinish();
 
   // Load 3 pages and wait. The 3rd one has a worker
   let page1 = await BrowserTestUtils.openNewForegroundTab({
-    gBrowser, opening: 'about:about', forceNewProcess: false
+    gBrowser, opening: "about:about", forceNewProcess: false
   });
 
   let page2 = await BrowserTestUtils.openNewForegroundTab({
-    gBrowser, opening: 'about:memory', forceNewProcess: false
-  });
-
-  let page3 = await BrowserTestUtils.openNewForegroundTab({
-    gBrowser, opening: "about:performance", forceNewProcess: true
+    gBrowser, opening: "about:memory", forceNewProcess: false
   });
 
   // load a 4th tab with a worker
@@ -108,10 +104,23 @@ add_task(async function test() {
     Assert.ok(parentProcessEvent, "parent process sent back some events");
     Assert.ok(isTopLevel, "example.com as a top level window");
     Assert.ok(aboutMemoryFound, "about:memory");
+
+    // Doing a second call, we shoud get bigger values
+    let previousWorkerDuration = workerDuration;
+    let previousWorkerTotal = workerTotal;
+    let previousDuration = duration;
+    let previousTotal = total;
+
+    results = await ChromeUtils.requestPerformanceMetrics();
+    exploreResults(results);
+
+    Assert.ok(workerDuration > previousWorkerDuration, "Worker duration should be positive");
+    Assert.ok(workerTotal > previousWorkerTotal, "Worker count should be positive");
+    Assert.ok(duration > previousDuration, "Duration should be positive");
+    Assert.ok(total > previousTotal, "Should get a positive count");
   });
 
   BrowserTestUtils.removeTab(page1);
   BrowserTestUtils.removeTab(page2);
-  BrowserTestUtils.removeTab(page3);
-  SpecialPowers.clearUserPref('dom.performance.enable_scheduler_timing');
+  SpecialPowers.clearUserPref("dom.performance.enable_scheduler_timing");
 });

dom/workers/WorkerDebugger.cpp

@@ -517,7 +517,6 @@ WorkerDebugger::ReportPerformanceInfo()
       return PerformanceInfo(uri->GetSpecOrDefault(), pid, pwid, duration,
                             true, isTopLevel, items);
     }
-    perf->ResetPerformanceCounters();
   }
 
   return PerformanceInfo(uri->GetSpecOrDefault(), pid, pwid, duration,

xpcom/tests/gtest/TestThreadMetrics.cpp

@@ -106,19 +106,7 @@ protected:
     mDispatchCount = (uint32_t)TaskCategory::Other + 1;
   }
 
-  void resetCounters() {
-    // let's reset the counters
-    mCounter->ResetPerformanceCounters();
-    for (uint32_t i = 0; i < mDispatchCount; i++) {
-      ASSERT_EQ(mCounter->GetDispatchCounter()[i], 0u);
-    }
-    ASSERT_EQ(mCounter->GetExecutionDuration(), 0u);
-  }
-
   virtual void TearDown() {
-    // let's reset the counters
-    resetCounters();
-
     // and remove the document from the doc group (actually, a nullptr)
     mDocGroup->RemoveDocument(nullptr);
     mDocGroup = nullptr;

xpcom/threads/PerformanceCounter.cpp

@@ -22,7 +22,6 @@ PerformanceCounter::PerformanceCounter(const nsACString& aName)
     mDispatchCounter(),
     mName(aName)
 {
-  ResetPerformanceCounters();
 }
 
 void
@@ -63,13 +62,3 @@ PerformanceCounter::GetDispatchCount(DispatchCategory aCategory)
 {
   return mDispatchCounter[aCategory.GetValue()];
 }
-
-void
-PerformanceCounter::ResetPerformanceCounters()
-{
-  for (auto& cnt : mDispatchCounter) {
-    cnt = 0;
-  }
-  mExecutionDuration = 0;
-  mTotalDispatchCount = 0;
-}

xpcom/threads/PerformanceCounter.h

@@ -80,12 +80,16 @@ public:
    * This is called everytime a runnable is dispatched.
    *
    * aCategory can be used to distinguish counts per TaskCategory
+   *
+   * Note that an overflow will simply reset the counter.
    */
   void IncrementDispatchCounter(DispatchCategory aCategory);
 
   /**
    * This is called via nsThread::ProcessNextEvent to measure runnable
    * execution duration.
+   *
+   * Note that an overflow will simply reset the counter.
    */
   void IncrementExecutionDuration(uint32_t aMicroseconds);
 
@@ -109,11 +113,6 @@ public:
    */
   uint64_t GetTotalDispatchCount();
 
-  /**
-   * Reset all counters and execution duration.
-   */
-  void ResetPerformanceCounters();
-
 private:
   ~PerformanceCounter() {}