[jira] [Assigned] (HBASE-4111) readBlock in HFile.Reader not 64 KB, but 5~6MB

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

     [ https://issues.apache.org/jira/browse/HBASE-4111?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

stack reassigned HBASE-4111:
----------------------------

    Assignee: Li Pi  (was: mingjian)

Assigning this to you Li, not because I'm saying you should fix this, but just so you know this thing exists; you are messing in this area and you might trip over it or know whats up here.

> readBlock in HFile.Reader not 64 KB, but 5~6MB
> ----------------------------------------------
>
>                 Key: HBASE-4111
>                 URL: https://issues.apache.org/jira/browse/HBASE-4111
>             Project: HBase
>          Issue Type: Bug
>          Components: io, regionserver
>            Reporter: mingjian
>            Assignee: Li Pi
>         Attachments: code and result.txt
>
>
>     We found a strange problem in our read test. 
>     It is a 5 nodes cluster.Four of our 5 regionservers set "hfile.block.cache.size"=0.4, one of them is 0.1(we call it node A). When we random read from a 2TB data table we found node A's network reached 100MB, and others are less than 10MB. So the read speed is low.
>     We set node A's "hfile.block.cache.size"=0.2, then all the nodes's network are 10MB, that's right. To find why is this we debug with btrace and find "readBlock" in HFile.Reader become abnormal.We know hbase read a block which is 64 KB from disks and put it into blockcache. But when we set "hfile.block.cache.size"=0.1, it is not 64KB, it is 5~6MB one time after about 1 minute we restart hbase.
>     Why not 64 KB? The btrace code and results are in the attachments. 

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