Copilot commented on code in PR #13115:
URL: https://github.com/apache/gluten/pull/13115#discussion_r4269303985
##########
cpp/velox/compute/VeloxBackend.cc:
##########
@@ -254,6 +255,10 @@ void VeloxBackend::init(
std::make_unique<folly::CPUThreadPoolExecutor>(ioThreads,
folly::CPUThreadPoolExecutor::makeLifoSemQueue());
}
+ const auto broadcastHashTableBuildThreads =
+ std::max<int32_t>(1,
backendConf_->get<int32_t>(kBroadcastHashTableBuildThreads,
numTaskSlotsPerExecutor));
+ broadcastHashTableBuildExecutor_ =
std::make_unique<folly::CPUThreadPoolExecutor>(broadcastHashTableBuildThreads);
Review Comment:
The dedicated `CPUThreadPoolExecutor` is created unconditionally during
`VeloxBackend::init()`, which adds at least one extra thread per backend
instance even if parallel broadcast build is never used. If thread
count/footprint is a concern in production deployments, consider
lazy-initializing this executor on first use (similar to the existing
`std::call_once` pattern mentioned in the PR description) or only creating it
when the feature/config requires it.
##########
cpp/velox/compute/VeloxBackend.cc:
##########
@@ -254,6 +255,10 @@ void VeloxBackend::init(
std::make_unique<folly::CPUThreadPoolExecutor>(ioThreads,
folly::CPUThreadPoolExecutor::makeLifoSemQueue());
}
+ const auto broadcastHashTableBuildThreads =
+ std::max<int32_t>(1,
backendConf_->get<int32_t>(kBroadcastHashTableBuildThreads,
numTaskSlotsPerExecutor));
+ broadcastHashTableBuildExecutor_ =
std::make_unique<folly::CPUThreadPoolExecutor>(broadcastHashTableBuildThreads);
Review Comment:
The PR description states that a configured value <= 0 should fall back to
`kNumTaskSlotsPerExecutor`, but the current logic treats an explicit 0 (or
negative) as `1` due to `std::max(1, value)`. This changes the
documented/advertised behavior for users who set the config to 0 expecting the
previous/default sizing. Consider reading the configured value first, and if it
is <= 0 then substitute `numTaskSlotsPerExecutor`, then apply the minimum-of-1
rule.
##########
gluten-ut/spark35/src/test/backends-velox/org/apache/spark/sql/execution/joins/GlutenParallelBroadcastJoinSuite.scala:
##########
@@ -0,0 +1,65 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.spark.sql.execution.joins
+
+import org.apache.gluten.execution.BroadcastHashJoinExecTransformer
+
+import org.apache.spark.SparkConf
+import org.apache.spark.sql.GlutenSQLTestsTrait
+import org.apache.spark.sql.execution.ColumnarBroadcastExchangeExec
+
+class GlutenParallelBroadcastJoinSuite extends GlutenSQLTestsTrait {
+
+ override def sparkConf: SparkConf = super.sparkConf
+ .set("spark.sql.adaptive.enabled", "false")
+ .set("spark.gluten.sql.columnar.backend.velox.IOThreads", "0")
+ .set("spark.gluten.velox.broadcast.build.targetBytesPerThread", "8KB")
+
+ for (buildOnDriver <- Seq(false, true)) {
+ testGluten(s"parallel broadcast hash table build with IO disabled,
driver=$buildOnDriver") {
+ withSQLConf(
+
"spark.gluten.sql.columnar.backend.velox.driverSideBroadcastHashTableBuild" ->
+ buildOnDriver.toString,
+ "spark.gluten.velox.minTableRowsForParallelJoinBuild" -> "1",
+
"spark.gluten.sql.columnar.backend.velox.broadcastHashTableBuildThreads" -> "1"
Review Comment:
This test configures the dedicated build thread pool size to `1`, but later
asserts `metrics(\"buildThreads\").value > 1`. With a single-thread pool, the
parallel build path is unlikely to report more than one build thread, making
the assertion inconsistent with the test setup. Set
`broadcastHashTableBuildThreads` to a value >= 2 (or omit it to use the default
sizing) so the test reliably validates the parallel build behavior.
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