Fix flaky DBTestUniversalCompaction.UniversalCompactionTrivialMoveTest2

Summary:
A previous fix to DBTestUniversalCompaction.UniversalCompactionTrivialMoveTest2 didn't address the right problem. The problem is L0->L0 compaction is not trivial move in the scenario, not parallel compactions. Fix this.
Closes https://github.com/facebook/rocksdb/pull/1911

Differential Revision: D4608955

Pulled By: siying

fbshipit-source-id: 7a712cb

db/db_universal_compaction_test.cc

@@ -1028,13 +1028,15 @@ TEST_P(DBTestUniversalCompaction, UniversalCompactionTrivialMoveTest1) {
 // Test that checks trivial move in universal compaction
 TEST_P(DBTestUniversalCompaction, UniversalCompactionTrivialMoveTest2) {
   int32_t trivial_move = 0;
-  int32_t non_trivial_move = 0;
   rocksdb::SyncPoint::GetInstance()->SetCallBack(
       "DBImpl::BackgroundCompaction:TrivialMove",
       [&](void* arg) { trivial_move++; });
   rocksdb::SyncPoint::GetInstance()->SetCallBack(
-      "DBImpl::BackgroundCompaction:NonTrivial",
-      [&](void* arg) { non_trivial_move++; });
+      "DBImpl::BackgroundCompaction:NonTrivial", [&](void* arg) {
+        ASSERT_TRUE(arg != nullptr);
+        int output_level = *(static_cast<int*>(arg));
+        ASSERT_EQ(output_level, 0);
+      });
 
   rocksdb::SyncPoint::GetInstance()->EnableProcessing();
 
@@ -1044,7 +1046,7 @@ TEST_P(DBTestUniversalCompaction, UniversalCompactionTrivialMoveTest2) {
   options.num_levels = 15;
   options.write_buffer_size = 100 << 10;  // 100KB
   options.level0_file_num_compaction_trigger = 8;
-  options.max_background_compactions = 1;
+  options.max_background_compactions = 2;
   options.target_file_size_base = 64 * 1024;
   DestroyAndReopen(options);
   CreateAndReopenWithCF({"pikachu"}, options);
@@ -1065,7 +1067,6 @@ TEST_P(DBTestUniversalCompaction, UniversalCompactionTrivialMoveTest2) {
   dbfull()->TEST_WaitForCompact();
 
   ASSERT_GT(trivial_move, 0);
-  ASSERT_EQ(non_trivial_move, 0);
 
   rocksdb::SyncPoint::GetInstance()->DisableProcessing();
 }