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From "Robert Engels" <>
Subject RE: FieldsReader synchronized access vs. ThreadLocal ?
Date Thu, 18 May 2006 18:08:58 GMT
As someone else pointed out, the proposed mods will only affect queries the
return a lot of Documents. If your test is only set up to return a few
documents (or possible none at all), then you will see no difference.

The fact that some of the CPUs were far less than 100%, and others were at
100% may be a good sign. How any query threads were you testing with?

-----Original Message-----
From: Peter Keegan []
Sent: Thursday, May 18, 2006 1:01 PM
Subject: Re: FieldsReader synchronized access vs. ThreadLocal ?


Sorry I missed your questions.

The test results seem hard to believe. Doubling the CPUs only increased
> through put by 20%??? Seems rather low for primarily a "read only" test.

I think this refers to the test I did on a 16 cpu (32 hyperthreaded) server.
This system was actually two 8 cpu systems cabled together on their
backplanes. I suspect that some tradeoffs were made in its design that
allowed for this flexibility which resulted in the minimal improvement in
the tests.

Peter did not seem to answer many of the follow-up questions (at least I
> could not find the answers) regarding whether or not the CPU usage was
> 100%.

On the 16-cpu system I noticed that load was not distributed very evenly -
some were near 100%, others were less than 10%. On the AMD Opteron servers,
the distribution was quite even and between 75-100%.

I look forward to your thoughts, and others - hopefully someone can run the
> test on a multiple CPU machine.
I built Lucene with your mod's and ran my test on the 8 cpu AMD Linux
server, but noticed no difference in query throughput. It would seem that
ThreadLocal could improve performance, but I think my bottlenecks are
elsewhere, like IndexInput.readVInt and inserting results in priority


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