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https://issues.apache.org/jira/browse/SOLR-665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12617654#action_12617654
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Fuad Efendi commented on SOLR-665:
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bq. The Solr admin pages will not give you exact measurements.
Yes, and I do not need exact measurements! It gives me averageTimePerRequest
which improved almost 10 times on production server. Should I right JUnit tests
and execute it in a single-threaded environment? Better is to use The Grinder,
but I don't have time and spare CPUs.
bq. Consider the following case: thread A performs a synchronized put, thread B
performs an unsynchronized get on the same key. B gets scheduled before A
completes, the returned value will be undefined.
the returned value is well defined: it is either null or correct value.
bq. That's exactly the case here - the update thread modifies the map
structurally!
Who cares? We are not iterating the map!
Anyway, I believe simplified ConcurrentLRU backed by ConcurrentHashMap is
easier to understand and troubleshoot...
bq. I don't see the point of the static popularityCounter... that looks like a
bug.
No, it is not a bug. it is virtually "checkpoint", like as a timer, one timer
for all instances. We can use System.currentTimeMillis() instead, but static
volatile long is faster.
About specific use case: yes... if someone has 0.5 seconds response time for
faceted queries I am very happy... I had 15 seconds before going with FIFO.
> 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: 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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