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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15721) Optimization in cloning cells into MSLAB
Date Wed, 05 Oct 2016 15:29:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15549067#comment-15549067
] 

stack commented on HBASE-15721:
-------------------------------

This sort of stuff is odd... how we intend to address it going forward?

   offset = KeyValueUtil.appendToByteArray(this.cell, buf, offset, false);

We are doing the above in the class named CellUtil.

This stuff is fine but when do we move away from depending on the keyvalue being serialized
in the old KeyValue way? When we going to do a Cell w/ a new layout! (smile). For example,
we remove this deprecation which seems to be a regression:

243	   * @deprecated Since 0.98.0.  Use Cell Interface instead.  Do not presume single backing
buffer.		
1244	   */	1243	   */
1245	  @Deprecated
 public byte [] getBuffer() {

+1 on this patch as is.


> Optimization in cloning cells into MSLAB
> ----------------------------------------
>
>                 Key: HBASE-15721
>                 URL: https://issues.apache.org/jira/browse/HBASE-15721
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 2.0.0
>
>         Attachments: HBASE-15721.patch, HBASE-15721_V2.patch, HBASE-15721_V3.patch, HBASE-15721_V4.patch
>
>
> Before cells added to memstore CSLM, there is a clone of cell after copying it to MSLAB
chunk area.  This is done not in an efficient way.
> {code}
> public static int appendToByteArray(final Cell cell, final byte[] output, final int offset)
{
>     int pos = offset;
>     pos = Bytes.putInt(output, pos, keyLength(cell));
>     pos = Bytes.putInt(output, pos, cell.getValueLength());
>     pos = appendKeyTo(cell, output, pos);
>     pos = CellUtil.copyValueTo(cell, output, pos);
>     if ((cell.getTagsLength() > 0)) {
>       pos = Bytes.putAsShort(output, pos, cell.getTagsLength());
>       pos = CellUtil.copyTagTo(cell, output, pos);
>     }
>     return pos;
>   }
> {code}
> Copied in 9 steps and we end up parsing all lengths.  When the cell implementation is
backed by a single byte[] (Like KeyValue) this can be done in single step copy.
> Also avoid lots of garbage while doing this MSLAB copy. With every cell, we used to create
a ByteRange instance to pass the allocated chunk + offset from MSLAB to Segment.  Now we can
make the MSLAB impl to do the allocation and copy of the cell so that one object creation
per cell addition can be avoided.



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