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From "Vladimir Rodionov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15493) Default ArrayList size may not be optimal for Mutation
Date Mon, 21 Mar 2016 18:20:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15204801#comment-15204801
] 

Vladimir Rodionov commented on HBASE-15493:
-------------------------------------------

[~ram_krish]
{quote}
I have been trying to make this more accurate atleast in the server side. In my case with
>10 columns per cell the arraylist expansion was creating lot of garbage. But not sure
if 2 is going to really help there. I know you are trying to take a middle man approach here
but still. But getting the most exact estimate is much more complex in these cases.
{quote}

new API method in Mutation? setMaxCellPerCF?

> Default ArrayList size may not be optimal for Mutation
> ------------------------------------------------------
>
>                 Key: HBASE-15493
>                 URL: https://issues.apache.org/jira/browse/HBASE-15493
>             Project: HBase
>          Issue Type: Improvement
>          Components: Client, regionserver
>    Affects Versions: 2.0.0
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
>             Fix For: 2.0.0
>
>         Attachments: HBASE-15493-v1.patch
>
>
> {code}
>   List<Cell> getCellList(byte[] family) {
>     List<Cell> list = this.familyMap.get(family);
>     if (list == null) {
>       list = new ArrayList<Cell>();
>     }
>     return list;
>   }
> {code}
> Creates list of size 10, this is up to 80 bytes per column family in mutation object.

> Suggested:
> {code}
>   List<Cell> getCellList(byte[] family) {
>     List<Cell> list = this.familyMap.get(family);
>     if (list == null) {
>       list = new ArrayList<Cell>(CELL_LIST_INITIAL_CAPACITY);
>     }
>     return list;
>   }
> {code}
> CELL_LIST_INITIAL_CAPACITY = 2 in the patch, this is debatable. For mutation where every
CF has 1 cell, this gives decent reduction in memory allocation rate in both client and server
during write workload. ~2%, not a big number, but as I said, already, memory optimization
will include many small steps.



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