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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2020/02/18 01:07:18 UTC
[GitHub] [flink] wsry commented on issue #11088: [FLINK-16012][runtime]
Reduce the default number of buffers per channel from 2 to 1
wsry commented on issue #11088: [FLINK-16012][runtime] Reduce the default number of buffers per channel from 2 to 1
URL: https://github.com/apache/flink/pull/11088#issuecomment-587227214
Theoretically, reducing the number of buffers may break the data processing pipeline which can influence the performance. For verification, I hava tested the change using the flink micro benchmark and a simple benchmark job. Unfortunately, regressions are seen for both tests.
For micro benchmark, the following are some results with regression (Because of the unstable result, I run each test three times.):
Using 2 buffer:
```
Benchmark (channelsFlushTimeout) (writers) Mode Cnt Score Error Units
networkThroughput 1000,100ms 1 thrpt 30 15972.952 ± 752.985 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 27650.498 ± 713.728 ops/ms
networkThroughput 1000,100ms 1 thrpt 30 15566.705 ± 2007.335 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 27769.195 ± 1632.614 ops/ms
networkThroughput 1000,100ms 1 thrpt 30 15598.175 ± 1671.515 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 27499.901 ± 1035.415 ops/ms
```
Using 1 buffer：
```
Benchmark (channelsFlushTimeout) (writers) Mode Cnt Score Error Units
networkThroughput 1000,100ms 1 thrpt 30 13116.610 ± 325.587 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 22837.502 ± 1024.360 ops/ms
networkThroughput 1000,100ms 1 thrpt 30 11924.883 ± 1038.508 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 22823.586 ± 892.918 ops/ms
networkThroughput 1000,100ms 1 thrpt 30 12960.345 ± 1596.465 ops/ms
networkThroughput 1000,100ms 4 thrpt 30 23028.803 ± 933.609 ops/ms
```
From the above results, we can see about 20% performance regression. For the benchmark job, there are also regressions (about 10% - 20%) in some cases where input channel numbers are small, for example 2 input channels, which means the number of buffer can be used is limited.
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