Merge pull request #7078 from dmitripivkine/master

Remove incorrect assertions and adjust stall time calculation
eclipse-openj9 · Jul 28, 2023 · f95ba19 · f95ba19
2 parents e5dabb6 + 7dbcda3
commit f95ba19
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Showing 2 changed files with 14 additions and 4 deletions.
diff --git a/gc/base/standard/ParallelScavengeTask.cpp b/gc/base/standard/ParallelScavengeTask.cpp
@@ -95,7 +95,6 @@ MM_ParallelScavengeTask::synchronizeGCThreadsAndReleaseMain(MM_EnvironmentBase *
 	}
 
 	/* _syncCriticalSectionDuration must be set now, this thread's stall time is at least the duration of critical section */
-	Assert_MM_true((endTime - startTime) >= _syncCriticalSectionDuration);
 	env->_scavengerStats.addToSyncStallTime(startTime, endTime, _syncCriticalSectionDuration);
 
 	return result;
@@ -117,7 +116,6 @@ MM_ParallelScavengeTask::synchronizeGCThreadsAndReleaseSingleThread(MM_Environme
 	}
 
 	/* _syncCriticalSectionDuration must be set now, this thread's stall time is at least the duration of critical section */
-	Assert_MM_true((endTime - startTime) >= _syncCriticalSectionDuration);
 	env->_scavengerStats.addToSyncStallTime(startTime, endTime, _syncCriticalSectionDuration);
 
 	return result;

diff --git a/gc/stats/ScavengerStats.hpp b/gc/stats/ScavengerStats.hpp
@@ -193,9 +193,21 @@ class MM_ScavengerStats
 	MMINLINE void 
 	addToSyncStallTime(uint64_t startTime, uint64_t endTime, uint64_t criticalSectionDuration = 0)
 	{
+		uint64_t criticalTime = criticalSectionDuration;
+		uint64_t deltaTime = endTime - startTime;
+
+		/*
+		 * criticalSectionDuration and deltaTime can be measured on clocks running on different cores asynchronously.
+		 * It means for close intervals (despite clocks are monotonic) criticalTime can be measured
+		 * slightly larger than deltaTime. So, criticalSectionDuration should be adjusted in this case.
+		 */
+		if (criticalTime > deltaTime) {
+			criticalTime = deltaTime;
+		}
+
 		_syncStallCount += 1;
-		_syncStallTime += (endTime - startTime);
-		_adjustedSyncStallTime += ((endTime - startTime) - criticalSectionDuration);
+		_syncStallTime += deltaTime;
+		_adjustedSyncStallTime += (deltaTime - criticalTime);
 	}
 
 	MMINLINE void