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From "Misty Stanley-Jones (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8315) Documentation should have more information of LRU Stats
Date Wed, 28 May 2014 23:20:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14011801#comment-14011801
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Misty Stanley-Jones commented on HBASE-8315:
--------------------------------------------

[~daisuke.kobayashi] Do you think this info is still current? Where did you envision it going
in the Ref Guide? I couldn't find a place where any of this is discussed currently.

> Documentation should have more information of LRU Stats
> -------------------------------------------------------
>
>                 Key: HBASE-8315
>                 URL: https://issues.apache.org/jira/browse/HBASE-8315
>             Project: HBase
>          Issue Type: Improvement
>          Components: documentation
>    Affects Versions: 0.95.0
>            Reporter: Daisuke Kobayashi
>            Assignee: Misty Stanley-Jones
>              Labels: documentation
>
> Unfortunately, there's no documentation to explain the meaning of each LRU Stats in the
regionserver logs.  So this is for creating a new paragraph regarding this.  My current idea
is below, but it's a little bit difficult to explain the difference between 'cachingAccesses'
and 'accesses' from an administrator or a user views.
> Could you guys help to improve the content?
> {noformat}
> total: The current memory size of the cache in use.
> free: The total free memory currently available to store more cache entries.
> max: Maximum allowed memory size of the cache.
> blocks: Caches store blocks of data; this number is the current # of blocks stored, which
use up the "total" memory space.
> accesses: The total number of times the cache was accessed, regardless of result.
> hits: The total number of times the cache was accessed and the result was a successful
hit (presence of looked up element in cache is a hit).
> hitRatio: The current percentage for "hits / accesses".
> ====
> Unclear:
> cachingAccesses: cachingHits + The number of getBlock requests that were cache misses,
but only from requests that were set to use the block cache.
> cachingHits: The number of getBlock requests that were cache hits, but only from requests
that were set to use the block cache. This is because all reads
> =====
> cachingHitsRatio: The current percentage for "cachintHits / cachingAccesses"
> evictions: The total number of times an eviction has occurred (based on the use of the
LRU algorithm)
> evicted: The total number of blocks that have been evicted (based on the use of the LRU
algorithm)
> evictedPerRun: The total number of blocks that have been evicted overall / The number
of times an eviction has occurred overall
> {noformat}
> And also, where should we add this paragraph in the documentation?



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