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From Apache Wiki <>
Subject [Lucene-java Wiki] Update of "ImproveSearchingSpeed" by MikeMcCandless
Date Wed, 24 Jun 2009 14:49:40 GMT
Dear Wiki user,

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The following page has been changed by MikeMcCandless:

The comment on the change is:
Add swappiness

   * '''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 (, 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.'''

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