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From "Daisuke Kobayashi (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-8315) Documentation should have more information of LRU Stats
Date Wed, 10 Apr 2013 01:05:13 GMT
Daisuke Kobayashi created HBASE-8315:
----------------------------------------

             Summary: 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


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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