Victsm commented on a change in pull request #25907: [SPARK-29206][SHUFFLE]
Make number of shuffle server threads a multiple of number of chunk fetch
handler threads.
URL: https://github.com/apache/spark/pull/25907#discussion_r329308432
##########
File path:
common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java
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@@ -111,8 +111,30 @@ public int numConnectionsPerPeer() {
/** Requested maximum length of the queue of incoming connections. Default
is 64. */
public int backLog() { return conf.getInt(SPARK_NETWORK_IO_BACKLOG_KEY, 64);
}
- /** Number of threads used in the server thread pool. Default to 0, which is
2x#cores. */
- public int serverThreads() { return
conf.getInt(SPARK_NETWORK_IO_SERVERTHREADS_KEY, 0); }
+ /**
+ * The configured ratio between number of server threads and number of chunk
fetch handler
+ * threads. Default to 1, which sets the size of both thread pools to be
equal. Number of
+ * server threads needs to be a multiple of this ratio. See SPARK-29206.
+ */
+ private int getChunkFetchHandlerThreadsRatio() {
+ return conf.getInt("spark.shuffle.server.chunkFetchHandlerThreadsRatio",
1);
+ }
+
+ /**
+ * Number of threads used in the server thread pool. Default to 0, which is
2x#cores.
+ * If spark.shuffle.server.chunkFetchHandlerThreadsRatio is configured, and
the Netty server
+ * is for shuffle, then the actual # of server threads will round up to the
nearest int that
+ * is a multiple of the configured ratio.
+ */
+ public int serverThreads() {
+ int configuredServerThreads =
conf.getInt(SPARK_NETWORK_IO_SERVERTHREADS_KEY, 0);
+ if (this.getModuleName().equalsIgnoreCase("shuffle")) {
+ int chunkFetchHandlerThreadsRatio = getChunkFetchHandlerThreadsRatio();
+ return (int) Math.ceil(configuredServerThreads /
(chunkFetchHandlerThreadsRatio * 1.0));
Review comment:
The reason for not applying
spark.shuffle.server.chunkFetchHandlerThreadsRatio when server threads is not
explicitly configured is because the behavior to set # server threads to 2 *
cores is inside Netty. We cannot guarantee 2 * cores can be divided by the
int_ratio or multiplier for a better name, unless we also overwrite the #
server threads when it's not configured.
I was previously thinking maybe the default behavior of server threads being
2 * cores should be preserved, but I think you are right in that if
spark.shuffle.server.chunkFetchHandlerThreadsRatio is configured, it should be
honored.
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