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https://issues.apache.org/jira/browse/FLINK-34148?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17819362#comment-17819362
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Sergey Nuyanzin commented on FLINK-34148:
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Seems I didn't get your initial question, sorry

yes that's a good question. 
To be honest I don't know the exact answer.
However what we have so far: 
1. I checked that it's reproducible only for jdk8 among LTS (didn't check 9, 
10) , e.g. for 11, 17 it is not reproducible, looks like it was fixed at some 
point on jdk level
2. I was not able to find any noticeable thing in profiler
3. Bisect shows that this perf regression comes with update of shading plugin 
(and changed behavior as mentioned above)
I tend to think that it could relate to something like classloading or SPI 
since without the fix amount of classes is bigger however as I mentioned this 
is only a hypotheses 
 

> Potential regression (Jan. 13): stringWrite with Java8
> ------------------------------------------------------
>
>                 Key: FLINK-34148
>                 URL: https://issues.apache.org/jira/browse/FLINK-34148
>             Project: Flink
>          Issue Type: Improvement
>          Components: API / Type Serialization System
>            Reporter: Zakelly Lan
>            Assignee: Sergey Nuyanzin
>            Priority: Blocker
>             Fix For: 1.19.0
>
>
> Significant drop of performance in stringWrite with Java8 from commit 
> [881062f352|https://github.com/apache/flink/commit/881062f352f8bf8c21ab7cbea95e111fd82fdf20]
>  to 
> [5d9d8748b6|https://github.com/apache/flink/commit/5d9d8748b64ff1a75964a5cd2857ab5061312b51]
>  . It only involves strings not so long (128 or 4).
> stringWrite.128.ascii(Java8) baseline=1089.107756 current_value=754.52452
> stringWrite.128.chinese(Java8) baseline=504.244575 current_value=295.358989
> stringWrite.128.russian(Java8) baseline=655.582639 current_value=421.030188
> stringWrite.4.chinese(Java8) baseline=9598.791964 current_value=6627.929927
> stringWrite.4.russian(Java8) baseline=11070.666415 current_value=8289.95767



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