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performance.
Description:
Replaced the old metadata cache with a cache with a modified LRU
replacement policy. This should improve the hit rate.
Solution:
Since we want to flush cache entries in increasing address order, I
used the threaded binary B-tree code to store the cache entries.
There is a fair bit of overhead here, so we may want to consider
other options.
While the code is designed to allow the support of other replacement
algorithms, at present, only a modified version of LRU is supported.
The modified LRU algorithm requires that a user selectable portion
of the cache entries be clean. The clean entries are evicted first
when writes are not permitted. If the pool of clean entries is used
up, the cache grows beyond its user specified maximum size. The
cache can also exceed its maximum size if the combined size of the
protected (or locked) entries exceeds the maximum size of the cache.
Platforms tested:
eirene (serial, parallel, fp), h5committested
Misc. update:
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