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https://issues.apache.org/jira/browse/FLINK-30073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17638058#comment-17638058
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Yun Tang commented on FLINK-30073:
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[~roman], the state.backend.rocksdb.memory.fixed-per-slot configuration is used
for expert mode, in which user could set the taskmanager.memory.managed.size as
zero and control the RocksDB's memory just as what they want.
In this case, user need to ensure on their own that enough memory is available
outside the JVM for RocksDB (you can refer to the 'Expert Mode' description in
https://nightlies.apache.org/flink/flink-docs-master/docs/ops/state/state_backends/#memory-management
). This is more like a configuration to keep backward compatibility for the
memory usage before flink-1.10.
> Managed memory can be wasted if RocksDB memory is fixed-per-slot
> ----------------------------------------------------------------
>
> Key: FLINK-30073
> URL: https://issues.apache.org/jira/browse/FLINK-30073
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Task
> Affects Versions: 1.16.0, 1.17.0, 1.15.2
> Reporter: Roman Khachatryan
> Priority: Major
>
> When
> [state.backend.rocksdb.memory.fixed-per-slot|https://github.com/apache/flink/blob/ba4b182955867fedfa9891bf0bf430e92eeab41a/flink-runtime/src/main/java/org/apache/flink/runtime/util/config/memory/ManagedMemoryUtils.java#L75]
> is set, RocksDB does not use managed memory (this option overrides the
> 'state.backend.rocksdb.memory.managed').
> However, the runtime [doesn't take this into
> account|https://github.com/apache/flink/blob/ba4b182955867fedfa9891bf0bf430e92eeab41a/flink-runtime/src/main/java/org/apache/flink/runtime/util/config/memory/ManagedMemoryUtils.java#L75]
> and still reserves the managed memory according to the configured weigths.
> cc: [~yunta]
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