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https://issues.apache.org/jira/browse/FLINK-4545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15902916#comment-15902916
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ASF GitHub Bot commented on FLINK-4545:
---------------------------------------
Github user NicoK commented on a diff in the pull request:
https://github.com/apache/flink/pull/3467#discussion_r105143643
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/LocalBufferPool.java
---
@@ -265,11 +281,15 @@ public String toString() {
//
------------------------------------------------------------------------
private void returnMemorySegment(MemorySegment segment) {
+ assert Thread.holdsLock(availableMemorySegments);
--- End diff --
Using synchronized again would impact performance, while assertions only do
when they are enabled which is the case in our unit tests (see
https://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#enableAssertions).
> Flink automatically manages TM network buffer
> ---------------------------------------------
>
> Key: FLINK-4545
> URL: https://issues.apache.org/jira/browse/FLINK-4545
> Project: Flink
> Issue Type: Wish
> Components: Network
> Reporter: Zhenzhong Xu
>
> Currently, the number of network buffer per task manager is preconfigured and
> the memory is pre-allocated through taskmanager.network.numberOfBuffers
> config. In a Job DAG with shuffle phase, this number can go up very high
> depends on the TM cluster size. The formula for calculating the buffer count
> is documented here
> (https://ci.apache.org/projects/flink/flink-docs-master/setup/config.html#configuring-the-network-buffers).
>
> #slots-per-TM^2 * #TMs * 4
> In a standalone deployment, we may need to control the task manager cluster
> size dynamically and then leverage the up-coming Flink feature to support
> scaling job parallelism/rescaling at runtime.
> If the buffer count config is static at runtime and cannot be changed without
> restarting task manager process, this may add latency and complexity for
> scaling process. I am wondering if there is already any discussion around
> whether the network buffer should be automatically managed by Flink or at
> least expose some API to allow it to be reconfigured. Let me know if there is
> any existing JIRA that I should follow.
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