Fix MockSharedArbitrationTest.ensureMemoryPoolMaxCapacity (#11470)

Summary:
global arbitration now runs in a separate thread. The stats updating is async to the main testing thread. So the check might be flaky in this test. Making sure global arbitration finishes before checking stats eliminates the flakiness.

Pull Request resolved: #11470

Reviewed By: xiaoxmeng

Differential Revision: D65613023

Pulled By: tanjialiang

fbshipit-source-id: 4a41fffc524b014424931f605a68f13f3375389a

velox/common/memory/SharedArbitrator.cpp

@@ -1384,7 +1384,6 @@ SharedArbitrator::GlobalArbitrationSection::GlobalArbitrationSection(
 SharedArbitrator::GlobalArbitrationSection::~GlobalArbitrationSection() {
   VELOX_CHECK(arbitrator_->globalArbitrationRunning_);
   arbitrator_->globalArbitrationRunning_ = false;
-  ;
 }
 
 std::string SharedArbitrator::kind() const {

velox/common/memory/tests/MockSharedArbitratorTest.cpp

@@ -2287,6 +2287,7 @@ TEST_F(MockSharedArbitrationTest, ensureMemoryPoolMaxCapacity) {
        memCapacity - memCapacity / 2,
        false,
        false}};
+
   for (const auto& testData : testSettings) {
     SCOPED_TRACE(testData.debugString());
     setupMemory(
@@ -2322,6 +2323,8 @@ TEST_F(MockSharedArbitrationTest, ensureMemoryPoolMaxCapacity) {
     } else if (testData.hasOtherTask) {
       ASSERT_EQ(otherOp->reclaimer()->stats().numReclaims, 0);
     }
+    test::SharedArbitratorTestHelper arbitratorHelper(arbitrator_);
+    arbitratorHelper.waitForGlobalArbitrationToFinish();
     if (testData.expectedSuccess &&
         (((testData.allocatedBytes + testData.requestBytes) >
           testData.poolMaxCapacity) ||