[jira] [Commented] (HBASE-8836) Separate reader and writer thread pool in RegionServer, so that write throughput will not be impacted when the read load is very high

["Nicolas Liochon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-8836?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13758918#comment-13758918 ] 

Nicolas Liochon commented on HBASE-8836:
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It's very interesting. Could you give some details on the issue itself?
You say: writes are getting slow because they have to wait for slow get. Could it be that we cannot have a lot of threads writing because there is a single WAL, so we should have 2 threads for writing, and the other for reading? How does it work if the put don't write into the WAL for example? 
I mean, if the operations have an immutable fixed time, whatever the order the final throughput (time to execute all the operations) won't change. So I would like to understand where you make the money here :-), and if it's a general improvement or specific to a load (you seem to say it's for cheap puts, expensive gets)

+1 to what Lars said as well on batch mutation and patch globally (it needs a little bit of rework ;-) ).
Note that the implementation should be much easier to do in trunk because of the pluggable scheduler.

As I said above, I think it's quite interesting, there is likely something to improve here.
                
> Separate reader and writer thread pool in RegionServer, so that write throughput will not be impacted when the read load is very high
> -------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-8836
>                 URL: https://issues.apache.org/jira/browse/HBASE-8836
>             Project: HBase
>          Issue Type: New Feature
>          Components: Performance, regionserver
>    Affects Versions: 0.94.8
>            Reporter: Tianying Chang
>            Assignee: Nicolas Liochon
>             Fix For: 0.98.0
>
>         Attachments: hbase-8836.patch, Hbase-8836-perfNumber.pdf
>
>
> We found that when the read load on a specific RS is high, the write throughput also get impacted dramatically, and even cause write data loss sometimes. We want to prioritize the write by putting them in a separate queue from the read request, so that slower read will not make fast write wait nu-necessarily long.

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