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From "Feng Honghua (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10263) make LruBlockCache single/multi/in-memory ratio user-configurable and provide preemptive mode for in-memory type block
Date Mon, 13 Jan 2014 02:08:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13869242#comment-13869242
] 

Feng Honghua commented on HBASE-10263:
--------------------------------------

[~vrodionov] : 
bq.I have always thought that artificial LruBlockCache divide on regular and in-memory zones
was not a good idea.
to some extent, I agree:-)
bq.The good cache implementation must sort all these things out itself
not quite...for some applications they need better latency for some table regardless of what
the table's access pattern is compared to other tables. treating all the tables the same way
and just letting the 'good' cache take care of all of these is not desirable for such applications.
for example think about the META table(which is the internal in-memory table)

> make LruBlockCache single/multi/in-memory ratio user-configurable and provide preemptive
mode for in-memory type block
> ----------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-10263
>                 URL: https://issues.apache.org/jira/browse/HBASE-10263
>             Project: HBase
>          Issue Type: Improvement
>          Components: io
>            Reporter: Feng Honghua
>            Assignee: Feng Honghua
>             Fix For: 0.98.0, 0.99.0
>
>         Attachments: HBASE-10263-trunk_v0.patch, HBASE-10263-trunk_v1.patch, HBASE-10263-trunk_v2.patch
>
>
> currently the single/multi/in-memory ratio in LruBlockCache is hardcoded 1:2:1, which
can lead to somewhat counter-intuition behavior for some user scenario where in-memory table's
read performance is much worse than ordinary table when two tables' data size is almost equal
and larger than regionserver's cache size (we ever did some such experiment and verified that
in-memory table random read performance is two times worse than ordinary table).
> this patch fixes above issue and provides:
> 1. make single/multi/in-memory ratio user-configurable
> 2. provide a configurable switch which can make in-memory block preemptive, by preemptive
means when this switch is on in-memory block can kick out any ordinary block to make room
until no ordinary block, when this switch is off (by default) the behavior is the same as
previous, using single/multi/in-memory ratio to determine evicting.
> by default, above two changes are both off and the behavior keeps the same as before
applying this patch. it's client/user's choice to determine whether or which behavior to use
by enabling one of these two enhancements.



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