Hi Shawn,

We found following  link
<https://www.google.com/url?q=http://lucene.472066.n3.nabble.com/CommitScheduler-Thread-blocked-due-to-excessive-number-of-Merging-Threads-td4353964.html&sa=D&source=hangouts&ust=1523527480128000&usg=AFQjCNENaNhq49nMSj8WtS_Qx-N4K23v0Q>  
where its mentioned like in 6.2.1 it's faster where as in 6.6 its slower.
Keep this, we too tried with 6.2.1 in our performance environment and we
found that CPU usage came down to 60 to 70% where as in 6.5.1 it was always
more than 95%

Settings are same and data size and indexing speed remains same. Pls check
the  JVM snapshot
<https://lh3.googleusercontent.com/-MHYsop5Vovo/Ws3V8KrT2VI/AAAAAAAAALI/GXmcWA4OtPQwwpF09scU5riJ1VHFOUtHQCL0BGAYYCw/h1080/2018-04-11.png>  
when we index using 6.2.1
Following is the  snapshot
<https://lh3.googleusercontent.com/-FoOmxYACbKc/Ws3gUQ323rI/AAAAAAAACeA/xdZedHlr1pcRbBrxhNJFPSvZqaH6rIoEACL0BGAYYCw/h363/2018-04-11.png>
taken with 6.5.1

Is there any reason why such a huge difference with CPU usage patterns
between 6.2.1 and 6.5.1 ?

Can we do something in 6.5.1 to make it as 6.2.1? Because we don't want to
downgrade to 6.2.1 from 6.5.1.

Let us know your thoughts on this.

Thanks and Regards,

--
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