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From Magnus Rundberget <run...@mac.com>
Subject Re: lucene nicking my memory ?
Date Wed, 03 Dec 2008 12:51:34 GMT
Sure,

Tried with the following
Java version: build 1.5.0_16-b06-284 (dev), 1.5.0_12 (production)
OS : Mac OS/X Leopard(dev) and Windows XP(dev), Windows 2003  
(production)
Container : Jetty 6.1 and Tomcat 5.5 (latter is used both in dev and  
production)


current jvm options
-Xms512m -Xmx1024M -XX:MaxPermSize=256m
... tried a few gc settings as well but nothing that has helped  
(rather slowed things down)

production hw running 2 XEON dual core processors

in production our memory reaches the 1024 limit after a while (a few  
hours) and at some point it stops responding to forced gc (using  
jconsole).

need to digg quite a bit more to figure out the exact prod settings.  
But safe to say the memory usage pattern can be recreated on different  
hardware configs, with different os's, different 1.5 jvms and  
different containers (jetty and tomcat).



cheers
Magnus



On 3. des.. 2008, at 13.10, Glen Newton wrote:

> Hi Magnus,
>
> Could you post the OS, version, RAM size, swapsize, Java VM version,
> hardware, #cores, VM command line parameters, etc? This can be very
> relevant.
>
> Have you tried other garbage collectors and/or tuning as described in
> http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html?
>
> 2008/12/3 Magnus Rundberget <rundis@mac.com>:
>> Hi,
>>
>> We have an application using Tomcat, Spring etc and Lucene 2.4.0.
>> Our index is about 100MB (in test) and has about 20 indexed fields.
>>
>> Performance is pretty good, but we are experiencing a very high  
>> usage of
>> memory when searching.
>>
>> Looking at JConsole during a somewhat silly scenario (but  
>> illustrates the
>> problem);
>> (Allocated 512 MB Min heap space, max 1024)
>>
>> 0. Initially memory usage is about 70MB
>> 1. Search for word "er", heap memory usage goes up by 100-150MB
>> 1.1 Wait for 30 seconds... memory usage stays the same (ie no gc)
>> 2. Search by word "og", heap memory usage goes up another 50-100MB
>> 2.1 See 1.1
>>
>> ...and so on until it seems to reach the 512 MB limit, and then a  
>> garbage
>> collection is performed
>> i.e garbage collection doesn't seem to occur until it "hits the roof"
>>
>> We believe the scenario is similar in production, were our heap  
>> space is
>> limited to 1.5 GB.
>>
>>
>> Our search is basically as follows
>> ----------------------------------------------
>> 1. Open an IndexSearcher
>> 2. Build a Boolean Query searching across 4 fields (title, summary,  
>> content
>> and daterangestring YYYYMMDD)
>> 2.1 Sort on title
>> 3. Perform search
>> 4. Iterate over hits to build a set of custom result objects  
>> (pretty small,
>> as we dont include content in these)
>> 5. Close searcher
>> 6. Return result objects.
>
> You should not close the searcher: it can be shared by all queries.
> What happens when you warm Lucene with a (large) number of queries: do
> things stabilize over time?
>
> A 100MB index is (relatively) very small for Lucene (I have indexes
>> 100GB). What kind of response times are you getting, independent of
> memory usage.
>
> -glen
>
>>
>> We have tried various options based on entries on this mailing list;
>> a) Cache the IndexSearcher - Same results
>> b) Remove sorting - Same result
>> c) In point 4 only iterating over a limited amount of hits rather  
>> than whole
>> collection - Same result in terms of memory usage, but obviously  
>> increased
>> performance
>> d) Using RamDirectory vs FSDirectory - Same result only initial  
>> heap usage
>> is higher using ramdirectory (in conjuction with cached  
>> indexsearcher)
>>
>>
>> Doing some profiling using YourKit shows a huge number of char[],  
>> int[] and
>> string[], and ever increasing number of lucene related objects.
>>
>>
>>
>> Reading through the mailing lists, suspicions are that our problem is
>> related to ThreadLocals and memory not being released. Noticed that  
>> there
>> was a related patch for this in 2.4.0, but it doesn't seem to help  
>> us much.
>>
>> Any ideas ?
>>
>> kind regards
>> Magnus
>>
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>>
>
>
>
> -- 
>
> -
>
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