Matthias Schwalbe created FLINK-26586:
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Summary: FileSystem uses unbuffered read I/O
Key: FLINK-26586
URL: https://issues.apache.org/jira/browse/FLINK-26586
Project: Flink
Issue Type: Improvement
Components: API / State Processor, Connectors / FileSystem, Runtime /
Checkpointing
Affects Versions: 1.14.0, 1.13.0
Reporter: Matthias Schwalbe
- I found out that, at least when using LocalFileSystem on a windows system,
read I/O to load a savepoint is unbuffered,
- See example stack [1]
- i.e. in order to load only a long in a serializer, it needs to go into
kernel mode 8 times and load the 8 bytes one by one
- I coded a BufferedFSDataInputStreamWrapper that allows to opt-in buffered
reads on any FileSystem implementation
- In our setting savepoint load is now 30 times faster
- I’ve once seen a Jira ticket as to improve savepoint load time in general
(lost the link unfortunately), maybe this approach can help with it
- not sure if HDFS has got the same problem
- I can contribute my implementation of a BufferedFSDataInputStreamWrapper
which can be integrated in any
[1] unbuffered reads stack:
read:207, FileInputStream (java.io)
read:68, LocalDataInputStream (org.apache.flink.core.fs.local)
read:50, FSDataInputStreamWrapper (org.apache.flink.core.fs)
read:42, ForwardingInputStream (org.apache.flink.runtime.util)
readInt:390, DataInputStream (java.io)
deserialize:80, BytePrimitiveArraySerializer
(org.apache.flink.api.common.typeutils.base.array)
next:298, FullSnapshotRestoreOperation$KeyGroupEntriesIterator
(org.apache.flink.runtime.state.restore)
next:273, FullSnapshotRestoreOperation$KeyGroupEntriesIterator
(org.apache.flink.runtime.state.restore)
restoreKVStateData:147, RocksDBFullRestoreOperation
(org.apache.flink.contrib.streaming.state.restore)
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