wsry opened a new pull request #15192:
URL: https://github.com/apache/flink/pull/15192
## What is the purpose of the change
Currently, the sort-merge shuffle implementation uses 4M unmanaged direct
memory as cache for data writing. This patch replaces the cache with writev
system call which can reduce the unmanaged direct memory usage without any
performance loss.
## Brief change log
- Remove the data writing cache in PartitionedFileWriter;
- Allocate a collection of network buffers as write buffer;
- Bulk write the data out when the write buffer is full.
## Verifying this change
This change is already covered by existing tests, such as
PartitionedFileWriteReadTest, SortMergeResultPartitionTest and
BlockingShuffleITCase.
## 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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