[FLINK-22307][network] Increase the default value of data writing cache size (not configurable) for sort-merge blocking shuffle

[wsry]

What is the purpose of the change

Currently, the data writing cache of sort-merge blocking shuffle is 8M, which can be not enough if data compression is enabled. This patch increases the cache size to 16M which can improve the performance for high compression ratio scenarios.

Brief change log

• Increase the data writing cache size of sort-merge blocking shuffle to 16M.

Verifying this change

This change is already covered by existing tests.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

• Does this pull request introduce a new feature? (yes / no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

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Automated Checks

Last check on commit b955af6 (Fri May 28 09:09:39 UTC 2021)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!
• This pull request references an unassigned Jira ticket. According to the code contribution guide, tickets need to be assigned before starting with the implementation work.

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Review Progress

• ❓ 1. The [description] looks good.
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• ❓ 3. Needs [attention] from.
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• ❓ 5. Overall code [quality] is good.

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CI report:

• 3d65a71 UNKNOWN
• c840d85 Azure: SUCCESS
• b955af6 UNKNOWN

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[guoweiM]

Thanks. LGTM.