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From "Esteban Gutierrez (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15180) Reduce garbage created while reading Cells from Codec Decoder
Date Fri, 29 Jan 2016 20:24:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15124141#comment-15124141
] 

Esteban Gutierrez commented on HBASE-15180:
-------------------------------------------

My guess at that time was that the rate the RSs where flushing the memstores aggressively,
MSLAB was only creating extra work for the collector. If I remember correctly, I remember
I started to notice the improvement of disabling MSLAB after going to higher throughputs (+100K
puts/sec). At lower throughputs I don't think the contribution with our without was noticeable.
 

> Reduce garbage created while reading Cells from Codec Decoder
> -------------------------------------------------------------
>
>                 Key: HBASE-15180
>                 URL: https://issues.apache.org/jira/browse/HBASE-15180
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0
>
>         Attachments: HBASE-15180.patch, HBASE-15180_V2.patch
>
>
> In KeyValueDecoder#parseCell (Default Codec decoder) we use KeyValueUtil#iscreate to
read cells from the InputStream. Here we 1st create a byte[] of length 4 and read the cell
length and then an array of Cell's length and read in cell bytes into it and create a KV.
> Actually in server we read the reqs into a byte[] and CellScanner is created on top of
a ByteArrayInputStream on top of this. By default in write path, we have MSLAB usage ON. So
while adding Cells to memstore, we will copy the Cell bytes to MSLAB memory chunks (default
2 MB size) and recreate Cells over that bytes.  So there is no issue if we create Cells over
the RPC read byte[] directly here in Decoder.  No need for 2 byte[] creation and copy for
every Cell in request.
> My plan is to make a Cell aware ByteArrayInputStream which can read Cells directly from
it.  
> Same Codec path is used in client side also. There better we can avoid this direct Cell
create and continue to do the copy to smaller byte[]s path.  Plan to introduce some thing
like a CodecContext associated with every Codec instance which can say the server/client context.



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