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