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From Jon Loken <jon.lo...@bipsolutions.com>
Subject RE: A model for predicting indexing memory costs?
Date Tue, 10 Mar 2009 15:32:51 GMT
Hi,

I haven't followed the whole thread, so pardon me if I am off topic.

In terms of OutOfMemoryExceptions, why not attempt to alleviate this in your code, rather
than overly relying on garbage collection. On other words: set big objects to null when you
are finished with them, in particular in loops. (like in C++)

What we do in the indexing loop is to set myDocument = null; etc. In addition, every n loops
we also do a garbage collection. Otherwise we would also have faced memory issues.

Jon

-----Original Message-----
From: Ian Lea [mailto:ian.lea@gmail.com]
Sent: 10 March 2009 10:54
To: java-user@lucene.apache.org
Subject: Re: A model for predicting indexing memory costs?

That's not the usual OOM message is it? java.lang.OutOfMemoryError: GC overhead limit exceeded.

Looks like you might be able to work round it with -XX:-UseGCOverheadLimit

http://java-monitor.com/forum/archive/index.php/t-54.html
http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#par_gc.oom


--
Ian.


On Tue, Mar 10, 2009 at 10:45 AM, mark harwood <markharw00d@yahoo.co.uk> wrote:
>
>>>But... how come setting IW's RAM buffer doesn't prevent the OOMs?
>
> I've been setting the IndexWriter RAM buffer to 300 meg and giving the JVM 1gig.
>
> Last run I gave the JVM 3 gig, with writer settings of  RAM buffer=300 meg, merge factor=20,
term interval=8192, usecompound=false. All fields are ANALYZED_NO_NORMS.
> Lucene version is a 2.9 build,  JVM is Sun 64bit 1.6.0_07.
>
> This graphic shows timings for 100 consecutive write sessions, each adding 30,000 documents,
committing and then closing :
>     http://tinyurl.com/anzcjw
> You can see the periodic merge costs and then a big spike towards the end before it crashed.
>
> The crash details are here after adding ~3 million documents in 98 write sessions:
>
> This batch index session added 3000 of 30000 docs : 10% complete
> Exception in thread "Thread-280" java.lang.OutOfMemoryError: GC
> overhead limit exceeded
>    at java.util.Arrays.copyOf(Unknown Source)
>    at java.lang.String..<init>(Unknown Source)
>    at
> org.apache.lucene.search.trie.TrieUtils.longToPrefixCoded(TrieUtils.ja
> va:148)
>    at
> org.apache.lucene.search.trie.TrieUtils.trieCodeLong(TrieUtils.java:30
> 2)
>    at
> test.LongTrieAnalyzer$LongTrieTokenStream.next(LongTrieAnalyzer.java:4
> 9)
>    at
> org.apache.lucene.index.DocInverterPerField.processFields(DocInverterP
> erField.java:159)
>    at
> org.apache.lucene.index.DocFieldConsumersPerField.processFields(DocFie
> ldConsumersPerField.java:36)
>    at
> org.apache.lucene.index.DocFieldProcessorPerThread.processDocument(Doc
> FieldProcessorPerThread.java:234)
>    at
> org.apache.lucene.index.DocumentsWriter.updateDocument(DocumentsWriter
> .java:762)
>    at
> org.apache.lucene.index.DocumentsWriter.addDocument(DocumentsWriter.ja
> va:740)
>    at
> org.apache.lucene.index.IndexWriter.addDocument(IndexWriter.java:2039)
>    at
> org.apache.lucene.index.IndexWriter.addDocument(IndexWriter.java:2013)
>    at test.IndexMarksFile$IndexingThread.run(IndexMarksFile.java:319)
> Exception in thread "Thread-281" java.lang.OutOfMemoryError: GC
> overhead limit exceeded
>    at org.apache.commons.csv.CharBuffer.toString(CharBuffer.java:177)
>    at org.apache.commons.csv.CSVParser.getLine(CSVParser.java:242)
>    at test.IndexMarksFile.getLuceneDocument(IndexMarksFile.java:272)
>    at test.IndexMarksFile$IndexingThread.run(IndexMarksFile.java:314)
> Committing
> Closing
> Exception in thread "main" java.lang.IllegalStateException: this
> writer hit an OutOfMemoryError; cannot commit
>    at
> org.apache.lucene.index.IndexWriter.prepareCommit(IndexWriter.java:356
> 9)
>    at
> org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3660)
>    at
> org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3634)
>    at test.IndexMarksFile.run(IndexMarksFile.java:176)
>    at test.IndexMarksFile.main(IndexMarksFile.java:101)
>    at test.MultiIndexAndRun.main(MultiIndexAndRun.java:49)
>
>
> For each write session I have a single writer, and 2 indexing threads adding documents
through this writer. There are no updates/deletes - only adds. When both indexing threads
complete the primary thread commits and closes the writer.
> I then open a searcher run some search benchmarks, close the searcher and start another
write session.
> The documents have ~12 fields and are all the same size so I don't think this OOM is
down to rogue data. Each field has 100 near-unique tokens.
>
> The files on disk after the crash are as follows:
>  1930004059 Mar  9 13:32 _106.fdt
>    2731084 Mar  9 13:32 _106.fdx
>        175 Mar  9 13:30 _106.fnm
>  1190042394 Mar  9 13:39 _106.frq
>  814748995 Mar  9 13:39 _106.prx
>   16512596 Mar  9 13:39 _106.tii
>  1151364311 Mar  9 13:39 _106.tis
>  1949444533 Mar  9 14:53 _139.fdt
>    2758580 Mar  9 14:53 _139.fdx
>        175 Mar  9 14:51 _139.fnm
>  1202044423 Mar  9 15:00 _139.frq
>  822954002 Mar  9 15:00 _139.prx
>   16629104 Mar  9 15:00 _139.tii
>  1159392207 Mar  9 15:00 _139.tis
>  1930102055 Mar  9 16:15 _16c.fdt
>    2731084 Mar  9 16:15 _16c.fdx
>        175 Mar  9 16:13 _16c.fnm
>  1190090014 Mar  9 16:22 _16c.frq
>  814763781 Mar  9 16:22 _16c.prx
>   16514967 Mar  9 16:22 _16c.tii
>  1151524173 Mar  9 16:22 _16c.tis
>  1928053697 Mar  9 17:52 _19e.fdt
>    2728260 Mar  9 17:52 _19e.fdx
>        175 Mar  9 17:46 _19e.fnm
>  1188837093 Mar  9 18:08 _19e.frq
>  813915820 Mar  9 18:08 _19e.prx
>   16501902 Mar  9 18:08 _19e.tii
>  1150623773 Mar  9 18:08 _19e.tis
>  1951474247 Mar  9 20:22 _1cj.fdt
>    2761396 Mar  9 20:22 _1cj.fdx
>        175 Mar  9 20:18 _1cj.fnm
>  1203285781 Mar  9 20:39 _1cj.frq
>  823797656 Mar  9 20:39 _1cj.prx
>   16639997 Mar  9 20:39 _1cj.tii
>  1160143978 Mar  9 20:39 _1cj.tis
>  1929978366 Mar 10 01:02 _1fm.fdt
>    2731060 Mar 10 01:02 _1fm.fdx
>        175 Mar 10 00:43 _1fm.fnm
>  1190031780 Mar 10 02:36 _1fm.frq
>  814741146 Mar 10 02:36 _1fm.prx
>   16513189 Mar 10 02:36 _1fm.tii
>  1151399139 Mar 10 02:36 _1fm.tis
>  189073186 Mar 10 01:51 _1ft.fdt
>     267556 Mar 10 01:51 _1ft.fdx
>        175 Mar 10 01:50 _1ft.fnm
>  110750150 Mar 10 02:04 _1ft.frq
>   79818488 Mar 10 02:04 _1ft.prx
>    2326691 Mar 10 02:04 _1ft.tii
>  165932844 Mar 10 02:04 _1ft.tis
>  212500024 Mar 10 03:16 _1g5.fdt
>     300684 Mar 10 03:16 _1g5.fdx
>        175 Mar 10 03:16 _1g5.fnm
>  125179984 Mar 10 03:28 _1g5.frq
>   89703062 Mar 10 03:28 _1g5.prx
>    2594360 Mar 10 03:28 _1g5.tii
>  184495760 Mar 10 03:28 _1g5.tis
>   64323505 Mar 10 04:09 _1gc.fdt
>      91020 Mar 10 04:09 _1gc.fdx
>  105283820 Mar 10 04:48 _1gf.fdt
>     148988 Mar 10 04:48 _1gf.fdx
>        175 Mar 10 04:09 _1gf.fnm
>       1491 Mar 10 04:09 _1gf.frq
>          4 Mar 10 04:09 _1gf.nrm
>       2388 Mar 10 04:09 _1gf.prx
>        254 Mar 10 04:09 _1gf.tii
>      15761 Mar 10 04:09 _1gf.tis
>  191035191 Mar 10 04:09 _1gg.fdt
>     270332 Mar 10 04:09 _1gg.fdx
>        175 Mar 10 04:09 _1gg.fnm
>  111958741 Mar 10 04:24 _1gg.frq
>   80645411 Mar 10 04:24 _1gg.prx
>    2349153 Mar 10 04:24 _1gg.tii
>  167494232 Mar 10 04:24 _1gg.tis
>        175 Mar 10 04:20 _1gh.fnm
>   10223275 Mar 10 04:20 _1gh.frq
>          4 Mar 10 04:20 _1gh.nrm
>    9056546 Mar 10 04:20 _1gh.prx
>     329012 Mar 10 04:20 _1gh.tii
>   23846511 Mar 10 04:20 _1gh.tis
>        175 Mar 10 04:28 _1gi.fnm
>   10221888 Mar 10 04:28 _1gi.frq
>          4 Mar 10 04:28 _1gi.nrm
>    9054280 Mar 10 04:28 _1gi.prx
>     328980 Mar 10 04:28 _1gi.tii
>   23843209 Mar 10 04:28 _1gi.tis
>        175 Mar 10 04:35 _1gj.fnm
>   10222776 Mar 10 04:35 _1gj.frq
>          4 Mar 10 04:35 _1gj.nrm
>    9054943 Mar 10 04:35 _1gj.prx
>     329060 Mar 10 04:35 _1gj.tii
>   23849395 Mar 10 04:35 _1gj.tis
>        175 Mar 10 04:42 _1gk.fnm
>   10220381 Mar 10 04:42 _1gk.frq
>          4 Mar 10 04:42 _1gk.nrm
>    9052810 Mar 10 04:42 _1gk.prx
>     329029 Mar 10 04:42 _1gk.tii
>   23845373 Mar 10 04:42 _1gk.tis
>        175 Mar 10 04:48 _1gl.fnm
>    9274170 Mar 10 04:48 _1gl.frq
>          4 Mar 10 04:48 _1gl.nrm
>    8226681 Mar 10 04:48 _1gl.prx
>     303327 Mar 10 04:48 _1gl.tii
>   21996826 Mar 10 04:48 _1gl.tis
>   22418126 Mar 10 04:58 _1gm.fdt
>      31732 Mar 10 04:58 _1gm.fdx
>        175 Mar 10 04:57 _1gm.fnm
>   10216672 Mar 10 04:57 _1gm.frq
>          4 Mar 10 04:57 _1gm.nrm
>    9049487 Mar 10 04:57 _1gm.prx
>     328813 Mar 10 04:57 _1gm.tii
>   23829627 Mar 10 04:57 _1gm.tis
>        175 Mar 10 04:58 _1gn.fnm
>     392014 Mar 10 04:58 _1gn.frq
>          4 Mar 10 04:58 _1gn.nrm
>     415225 Mar 10 04:58 _1gn.prx
>      24695 Mar 10 04:58 _1gn.tii
>    1816750 Mar 10 04:58 _1gn.tis
>        683 Mar 10 04:58 segments_7t
>         20 Mar 10 04:58 segments.gen
>  1935727800 Mar  9 11:17 _u1.fdt
>    2739180 Mar  9 11:17 _u1.fdx
>        175 Mar  9 11:15 _u1.fnm
>  1193583522 Mar  9 11:25 _u1.frq
>  817164507 Mar  9 11:25 _u1.prx
>   16547464 Mar  9 11:25 _u1..tii
>  1153764013 Mar  9 11:25 _u1.tis
>  1949493315 Mar  9 12:21 _x3.fdt
>    2758580 Mar  9 12:21 _x3.fdx
>        175 Mar  9 12:18 _x3.fnm
>  1202068425 Mar  9 12:29 _x3.frq
>  822963200 Mar  9 12:29 _x3.prx
>   16629485 Mar  9 12:29 _x3.tii
>  1159419149 Mar  9 12:29 _x3.tis
>
>
> Any ideas? I'm out of settings to tweak here.
>
> Cheers,
> Mark
>
>
>
>
> ----- Original Message ----
> From: Michael McCandless <lucene@mikemccandless.com>
> To: java-user@lucene.apache.org
> Sent: Tuesday, 10 March, 2009 0:01:30
> Subject: Re: A model for predicting indexing memory costs?
>
>
> mark harwood wrote:
>
>>
>> I've been building a large index (hundreds of millions) with mainly structured data
which consists of several fields with mostly unique values.
>> I've been hitting out of memory issues when doing periodic commits/closes which I
suspect is down to the sheer number of terms.
>>
>> I set the IndexWriter..setTermIndexInterval to 8 times the normal size of 128 (an
intervalof 1024) which delayed the onset of the issue but still failed.
>
> I think that setting won't change how much RAM is used when writing.
>
>> I'd like to get a little more scientific about what to set here rather than simply
experimenting with settings and hoping it doesn't fail again.
>>
>> Does anyone have a decent model worked out for how much memory is consumed at peak?
I'm guessing the contributing factors are:
>>
>> * Numbers of fields
>> * Numbers of unique terms per field
>> * Numbers of segments?
>
> Number of net unique terms (across all fields) is a big driver, but also net number of
term occurrences, and how many docs.  Lots of tiny docs take more RAM than fewer large docs,
when # occurrences are equal.
>
> But... how come setting IW's RAM buffer doesn't prevent the OOMs?  IW should simply flush
when it's used that much RAM.
>
> I don't think number of segments is a factor.
>
> Though mergeFactor is, since during merging the SegmentMerger holds SegmentReaders open,
and int[] maps (if there are any deletes) for each segment.  Do you have a large merge taking
place when you hit the OOMs?
>
> Mike
>
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