[jira] [Commented] (IGNITE-2408) Hot spot in GridDhtAtomicCache$DeferredResponseBuffer.addResponse()

["Vladimir Ozerov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IGNITE-2408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15125887#comment-15125887 ] 

Vladimir Ozerov commented on IGNITE-2408:
-----------------------------------------

I do not think we should do anything with concurrency here for now. Hotspot I observed was from ConcurrentLinedDeque8.size() method. Changing it to sizex() resolves the hotspot. 

> Hot spot in GridDhtAtomicCache$DeferredResponseBuffer.addResponse()
> -------------------------------------------------------------------
>
>                 Key: IGNITE-2408
>                 URL: https://issues.apache.org/jira/browse/IGNITE-2408
>             Project: Ignite
>          Issue Type: Sub-task
>          Components: cache
>    Affects Versions: 1.5.0.final
>            Reporter: Vladimir Ozerov
>            Assignee: Ilya Lantukh
>            Priority: Critical
>             Fix For: 1.6
>
>
> Problems:
> 1) DeferredResponseBuffer.respVers is ConcurrentLinkedDeque8 and size() method is called on it. It is O(N) for this collection, hence the hot spot.
> 2) We use read-write lock for very small updates. This is not efficient.
> Probably we should simply switch to (sycnhronized + ArrayList) and this will be enough. 
> If synchronized is not an option, at the very least we must use collection with O(1) size or maintain separate counter (e.g. LongAccumulator).



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