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https://issues.apache.org/jira/browse/SOLR-665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12618064#action_12618064
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Noble Paul commented on SOLR-665:
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There are a few obvious issues w/ your patch.
Effendi your implementation is wrong
{code:java}
if (wrapper.lastAccessed < pointer.lastAccessed) {
ref.set(new Pointer(key, wrapper.lastAccessed));
}
{code}
will always evaluate to true. We must be removing the entry which was accessed
first (not last)
. To get that you must maintian a linkedlist the way linkedhashmap maintains.
No other shortcut. Keeping one reference *will not* work.
In that implementation there is always a contention on the head so gets are
bound to be slow. That is why i did not go that route
And the static volatile counter is not threadsafe.
There is no need to use a WeakReference anywhere. This is a cache. So it *must*
maintain strong reference
> FIFO Cache (Unsynchronized): 9x times performance boost
> -------------------------------------------------------
>
> Key: SOLR-665
> URL: https://issues.apache.org/jira/browse/SOLR-665
> Project: Solr
> Issue Type: Improvement
> Affects Versions: 1.3
> Environment: JRockit R27 (Java 6)
> Reporter: Fuad Efendi
> Attachments: ConcurrentFIFOCache.java, ConcurrentFIFOCache.java,
> ConcurrentLRUCache.java, ConcurrentLRUWeakCache.java,
> ConcurrentLRUWeakCache.java, ConcurrentLRUWeakCache.java, FIFOCache.java
>
> Original Estimate: 672h
> Remaining Estimate: 672h
>
> Attached is modified version of LRUCache where
> 1. map = new LinkedHashMap(initialSize, 0.75f, false) - so that
> "reordering"/true (performance bottleneck of LRU) is replaced to
> "insertion-order"/false (so that it became FIFO)
> 2. Almost all (absolutely unneccessary) synchronized statements commented out
> See discussion at
> http://www.nabble.com/LRUCache---synchronized%21--td16439831.html
> Performance metrics (taken from SOLR Admin):
> LRU
> Requests: 7638
> Average Time-Per-Request: 15300
> Average Request-per-Second: 0.06
> FIFO:
> Requests: 3355
> Average Time-Per-Request: 1610
> Average Request-per-Second: 0.11
> Performance increased 9 times which roughly corresponds to a number of CPU in
> a system, http://www.tokenizer.org/ (Shopping Search Engine at Tokenizer.org)
> Current number of documents: 7494689
> name: filterCache
> class: org.apache.solr.search.LRUCache
> version: 1.0
> description: LRU Cache(maxSize=10000000, initialSize=1000)
> stats: lookups : 15966954582
> hits : 16391851546
> hitratio : 0.102
> inserts : 4246120
> evictions : 0
> size : 2668705
> cumulative_lookups : 16415839763
> cumulative_hits : 16411608101
> cumulative_hitratio : 0.99
> cumulative_inserts : 4246246
> cumulative_evictions : 0
> Thanks
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