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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5602) Add cache access pattern statistics and report hot blocks/keys
Date Tue, 20 Mar 2012 01:35:37 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13233101#comment-13233101
] 

Todd Lipcon commented on HBASE-5602:
------------------------------------

An alternative cache metric that would be interesting to know is the last access time of the
entries being evicted. If the last-access-time is only a minute or so, it's likely that you
can benefit from adding more cache. If it's substantially older, then adding cache won't really
help. http://en.wikipedia.org/wiki/Five-minute_rule
                
> Add cache access pattern statistics and report hot blocks/keys
> --------------------------------------------------------------
>
>                 Key: HBASE-5602
>                 URL: https://issues.apache.org/jira/browse/HBASE-5602
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Mikhail Bautin
>
> In many practical applications it would be very useful to know how well utilized the
block cache is, i.e. how many times we actually access a block once it gets into cache. This
would also allow to evaluate cache-on-write on flush. In addition, we need to keep track of
and report some set of hottest block in cache, and possibly even hottest keys. This would
allow to diagnose "hot-row" problems in real time.

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