[GitHub] [incubator-pekko] migesok commented on a diff in pull request #485: [DRAFT] support jdk9 forkjoinpool maximum-pool-size

["migesok (via GitHub)" <gi...@apache.org>]

migesok commented on code in PR #485:
URL: https://github.com/apache/incubator-pekko/pull/485#discussion_r1265117570


##########
actor/src/main/resources/reference.conf:
##########
@@ -482,6 +482,10 @@ pekko {
         # Setting to "FIFO" to use queue like peeking mode which "poll" or "LIFO" to use stack
         # like peeking mode which "pop".
         task-peeking-mode = "FIFO"
+
+        # This config is new in Pekko v1.1.0 and only has an effect if you are running with JDK 9 and above.
+        # Read the documentation on `java.util.concurrent.ForkJoinPool` to find out more. Default in hex is 0x7fff.
+        maximum-pool-size = 32767

Review Comment:
   May be it makes sense to make to turn around the configuration for FJP and make it similar to how the default global FJP in JDK is configured:
   - "parallelism" calculation could stay the same, be derived from runtime CPU count
   - add a new parameter called something like `max-spare-threads` (similar to "java.util.concurrent.ForkJoinPool.common.maximumSpares" system property) with 256 as the default value (again the same as the default for the global FJP)
   - the resulting maximum pool size will be calculated as parallelism + max-spare-threads
   
   Additionally I think another parameter needs to be exposed - `reject-blocking-if-pool-saturated` or something similar which governs the `saturate` predicate in the new FJP constructor - the user should have a choice between failing on blocking task once the pool limit is reached or keep piling the tasks in memory.
   
   Does it make sense?



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