[HBASE-8315] Documentation should have more information of LRU Stats

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.95.0
• Fix Version/s: 0.99.0
• Component/s: documentation
• Labels: documentation
• Assignee: M Linville
• Reporter: Daisuke Kobayashi
• Created: 10/Apr/13 01:03
• Updated: 21/Feb/15 23:30
• Resolved: 13/Jun/14 18:03

Description

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?

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

And also, where should we add this paragraph in the documentation?