[Lucene-java Wiki] Update of "ImproveSearchingSpeed" by MikeMcCandless

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The following page has been changed by MikeMcCandless:
http://wiki.apache.org/lucene-java/ImproveSearchingSpeed

The comment on the change is:
Add swappiness

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   * '''Get faster hardware, especially a faster IO system.'''
  
   Flash-based Solid State Drives works very well for Lucene searches. As seek-times for SSD's are about 100 times faster than traditional platter-based harddrives, the usual penalty for seeking is virtually eliminated. This means that SSD-equipped machines need less RAM for file caching and that searchers require less warm-up time before they respond quickly.
+ 
+  * '''Tune the OS'''
+ 
+  One tunable that stands out on Linux is swappiness (http://kerneltrap.org/node/3000), which controls how aggressively the OS will swap out RAM used by processes in favor of the IO Cache.  Most Linux distros default this to a highish number (meaning, aggressive) but this can easily cause horrible search latency, especially if you are searching a large index with a low query rate.  Experiment by turning swappiness down or off entirely (by setting it to 0).  Windows also has a checkbox, under My Computer -> Properties -> Advanced -> Performance Settings -> Advanced -> Memory Usage, that lets you favor Programs or System Cache, that's likely doing something similar.
  
   * '''Open the IndexReader with readOnly=true.'''