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From Doug Cutting <>
Subject Re: Lucene performance bottlenecks
Date Fri, 02 Dec 2005 18:36:03 GMT
Andrzej Bialecki wrote:
> For a simple TermQuery, if the DF(term) is above 10%, the response time 
> from is around 400ms (repeatable, after warm-up). 
> For such complex phrase queries the response time is around 1 sec or 
> more (again, after warm-up).

Are you specifying -server to the JVM?

> I tracked 
> the bottleneck to the scorers (see my previous email on this), but also 
> to IndexInput.readVInt.. 

It might be interesting to benchmark GCJ-compiled Lucene, since 
IndexInput.readVInt is highly optimized there.

> What's even more curious, most of the heap is 
> unused - I had the impression that Lucene tries to read as much of the 
> index as it can to memory in order to speed up the access, but 
> apparently that's not the case. The heap consumption was always in the 
> order of 100-200MB, no matter how large heap I set (and I tried values 
> between 1-4GB).

Lucene relies on the kernel to cache i/o, outside of the Java heap.


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