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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12295) Prevent block eviction under us if reads are in progress from the BBs
Date Fri, 17 Jul 2015 20:25:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14631844#comment-14631844
] 

stack commented on HBASE-12295:
-------------------------------

[~anoop.hbase] Anything to cut down on the combinatorial explosion.

bq. In read path we will deal with Cell type and we can add this to Cell interface.

Server-side only?

"May be we can avoid 2 impls one with out tags and one with. Have a state (boolean) in Cell
impl. We have SizeCachedKeyValue abd SizeCachedNoTagsKeyValue now. May be we will only have
SizeCachedKeyValue and it will have a boolean state whether it has tags or not. The getTagsLength()
can check this state ad return 0 or decode tags length. We have extra 6 bytes per cell in
this SizeCachedKeyValue now. Make it 7 is ok IMO"

Above seems fine though just one-byte we should profile; stuff might run better if padding
-- TBD. More ideal would be the case where if no tags, then no cost but don't know how to
do that.

> Prevent block eviction under us if reads are in progress from the BBs
> ---------------------------------------------------------------------
>
>                 Key: HBASE-12295
>                 URL: https://issues.apache.org/jira/browse/HBASE-12295
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver, Scanners
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 2.0.0
>
>         Attachments: HBASE-12295.pdf, HBASE-12295_1.patch, HBASE-12295_1.pdf, HBASE-12295_10.patch,
HBASE-12295_12.patch, HBASE-12295_14.patch, HBASE-12295_15.patch, HBASE-12295_16.patch, HBASE-12295_16.patch,
HBASE-12295_17.patch, HBASE-12295_2.patch, HBASE-12295_4.patch, HBASE-12295_4.pdf, HBASE-12295_5.pdf,
HBASE-12295_9.patch, HBASE-12295_trunk.patch
>
>
> While we try to serve the reads from the BBs directly from the block cache, we need to
ensure that the blocks does not get evicted under us while reading.  This JIRA is to discuss
and implement a strategy for the same.



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