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https://issues.apache.org/jira/browse/HBASE-9467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13764010#comment-13764010
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stack commented on HBASE-9467:
------------------------------

bq. Basically, if the load is CPU bound (a search in a cache), having more 
threads than core is nearly useless

It would be worse than useless?  They get in the way?

This sounds like good stuff [~nkeywal]

Lets just do [~tlipcon] suggestion -- would be good if calls only got as far as 
the front door mat and not into the parlor before we sent then back to where 
they came from.
                
> write can be totally blocked temporarily by a write-heavy region
> ----------------------------------------------------------------
>
>                 Key: HBASE-9467
>                 URL: https://issues.apache.org/jira/browse/HBASE-9467
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Feng Honghua
>            Priority: Minor
>
> Write to a region can be blocked temporarily if the memstore of that region 
> reaches the threshold(hbase.hregion.memstore.block.multiplier * 
> hbase.hregion.flush.size) until the memstore of that region is flushed.
> For a write-heavy region, if its write requests saturates all the handler 
> threads of that RS when write blocking for that region occurs, requests of 
> other regions/tables to that RS also can't be served due to no available 
> handler threads...until the pending writes of that write-heavy region are 
> served after the flush is done. Hence during this time period, from the RS 
> perspective it can't serve any request from any table/region just due to a 
> single write-heavy region.
> This sounds not very reasonable, right? Maybe write requests from a region 
> can only be served by a sub-set of the handler threads, and then write 
> blocking of any single region can't lead to the scenario mentioned above?
> Comment?

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