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https://issues.apache.org/jira/browse/FLINK-16057?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17115957#comment-17115957
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Roman Khachatryan commented on FLINK-16057:
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I was able to reproduce the above results both locally and on
codespeed.dak8s.net (*newer* version being faster).
The benchmark: [https://github.com/dataArtisans/flink-benchmarks/pull/62]
> Performance regression in ContinuousFileReaderOperator
> ------------------------------------------------------
>
> Key: FLINK-16057
> URL: https://issues.apache.org/jira/browse/FLINK-16057
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream, Runtime / Task
> Affects Versions: 1.11.0
> Reporter: Roman Khachatryan
> Assignee: Roman Khachatryan
> Priority: Blocker
> Labels: pull-request-available
> Fix For: 1.11.0
>
> Time Spent: 20m
> Remaining Estimate: 0h
>
> After switching CFRO to a single-threaded execution model performance
> regression was expected to be about 15-20% (benchmarked in November).
> But after merging to master it turned out to be about 50%.
>
> One reason is that the chaining strategy isn't set by default in CFRO factory.
> Without that even reading and outputting all records of a split in a single
> mail action doesn't reverse the regression (only about half).
> However, with strategy set AND batching enabled fixes the regression
> (starting from batch size 6).
> Though batching can't be used in practice because it can significantly delay
> checkpointing.
>
> Another approach would be to process one record and the repeat until
> defaultMailboxActionAvailable OR haveNewMail.
> This reverses regression and even improves the performance by about 50%
> compared to the old version.
>
> The final solution could also be FLIP-27.
>
> Other things tried (didn't help):
> * CFRO rework without subsequent commits (removing checkpoint lock)
> * different batch sizes, including the whole split, without chaining
> strategy fixed - partial improvement only
> * disabling close
> * disabling checkpointing
> * disabling output (serialization)
> * using LinkedList instead of PriorityQueue
>
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