[jira] [Commented] (HBASE-5602) Add cache access pattern statistics and report hot blocks/keys

["Todd Lipcon (Commented) (JIRA)" <ji...@apache.org>]

    [ 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:
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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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