[GitHub] srowen commented on a change in pull request #23278: [SPARK-24920][Core] Allow sharing Netty's memory pool allocators

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srowen commented on a change in pull request #23278: [SPARK-24920][Core] Allow sharing Netty's memory pool allocators
URL: https://github.com/apache/spark/pull/23278#discussion_r244815004
 
 

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 File path: common/network-common/src/main/java/org/apache/spark/network/util/TransportConf.java
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 @@ -265,6 +265,16 @@ public boolean saslServerAlwaysEncrypt() {
     return conf.getBoolean("spark.network.sasl.serverAlwaysEncrypt", false);
   }
 
+  /**
+   * Flag indicating whether to share the pooled ByteBuf allocators between the different Netty
+   * channels. If enabled then only two pooled ByteBuf allocators are created: one where caching
+   * is allowed (for transport servers) and one where not (for transport clients).
+   * When disabled a new allocator is created for each transport servers and clients.
+   */
+  public Boolean sharedByteBufAllocators() {
+    return conf.getBoolean("spark.network.sharedByteBufAllocators.enabled", true);
 
 Review comment:
   I'm not clear the comment above was using this change.
   I'm still not sure if there's a meaningful case where you'd not enable sharing, if it should always be a win and we don't know of any problems it causes (i.e. tests pass). I'm not against leaving the flag in, just adds to the number of configs we document, maintain, etc. I wouldn't mind removing it too, as I'm not sure when a user could decide this was something they don't want.
   
   For `spark.network.sharedByteBufAllocators.io.preferDirectBufs`, how about just using `spark.network.io.preferDirectBufs` which exists already? again same question... when would you want these set differently?

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