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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17917) Use pread by default for all user scan
Date Wed, 03 May 2017 10:24:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17917?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15994633#comment-15994633
] 

Duo Zhang commented on HBASE-17917:
-----------------------------------

Test command
{noformat}
./bin/hbase pe --rows=1000000 --cacheBlocks=false --caching=30 --scanReadType=pread/stream/default
--nomapred scan 10
{noformat}

|| ReadType || %us || RS %CPU || DN %CPU ||
| pread | 16 | 400 | 160 |
| stream | 13 | 390 | 30 |
| default | 13 | 390 | 30 |

So for reading the data of the whole region, streaming read will be better(as now we will
open a separated reader for streaming read). The main difference is at DN side, we can save
lots of seeks when using streaming read so the %CPU of DN will be much less.

Let me run the random scan test.

> Use pread by default for all user scan
> --------------------------------------
>
>                 Key: HBASE-17917
>                 URL: https://issues.apache.org/jira/browse/HBASE-17917
>             Project: HBase
>          Issue Type: Sub-task
>          Components: scan
>    Affects Versions: 2.0.0
>            Reporter: Duo Zhang
>            Assignee: Duo Zhang
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17917.patch, HBASE-17917-v1.patch, HBASE-17917-v2.patch, HBASE-17917-v2.patch,
HBASE-17917-v3.patch, HBASE-17917-v4.patch, HBASE-17917-v5.patch
>
>
> As said in the parent issue. We need some benchmark here first.



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