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From Paul Taylor <>
Subject Unable to improve performance
Date Fri, 27 Mar 2009 11:07:13 GMT

I am trying to run the performance tests against lucene, and am suprised 
about the results.

I have a test that creates a queue of queries, and a number of threads. 
The threads run concurrently getting the next query available, peforming 
a query on the index and taking the top hits. The index is 2GB in size, 
and was originally created froma database table of about 7 millions rows.

I ran the test a number of times with 30 threads, and max memory of 
3500mb I was processing 10,000 records in about 43 seconds ( 233 
queries/second) , the index was stored on a solid state drive running on 
a MacBook Pro (2.66 Ghz Intel Core 2 Duo, 4GB DDR). I dont really have a 
view on whether this is a good result or not but I was keen to try a few 
other things to see if I could improve performance further, but all my 
efforts have had minimal effect.

I tried creating a RAMDirectory based on the file index, once the index 
had been created (4 min 20 seconds) it again took
I copied the index to a slower external convention hard drive and it 
still took 43 seconds.

Reducing/increasing the memory allocated and the number of threads had 
minimal impact.

The main thing Im suprised about is I was expecting a massive difference 
in holding the index in memory instead on disk

thanks Paul

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