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From Yongtao Liu <liu...@gmail.com>
Subject Re: FW: MMapDirectory failed to map a 23G compound index segment
Date Wed, 21 Sep 2011 17:37:51 GMT
I hit similar issue recently.
Not sure if MMapDirectory is right way to go.

When index file be map to ram, JVM will call OS file mapping function.
The memory usage is in share memory, it may not be calculate to JVM process
space.

I saw one problem is if the index file bigger then physical ram, and there
are lot of query which cause wide index file access.
Then, the machine has no available memory.
The system change to very slow.

What i did is change lucene code to disable MMapDirectory.

On Wed, Sep 21, 2011 at 1:26 PM, Yongtao Liu <yliu@commvault.com> wrote:

>
>
> -----Original Message-----
> From: Michael McCandless [mailto:lucene@mikemccandless.com]
> Sent: Tuesday, September 20, 2011 3:33 PM
> To: solr-user@lucene.apache.org
> Subject: Re: MMapDirectory failed to map a 23G compound index segment
>
> Since you hit OOME during mmap, I think this is an OS issue not a JVM
> issue.  Ie, the JVM isn't running out of memory.
>
> How many segments were in the unoptimized index?  It's possible the OS
> rejected the mmap because of process limits.  Run "cat
> /proc/sys/vm/max_map_count" to see how many mmaps are allowed.
>
> Or: is it possible you reopened the reader several times against the index
> (ie, after committing from Solr)?  If so, I think 2.9.x never unmaps the
> mapped areas, and so this would "accumulate" against the system limit.
>
> > My memory of this is a little rusty but isn't mmap also limited by mem +
> swap on the box? What does 'free -g' report?
>
> I don't think this should be the case; you are using a 64 bit OS/JVM so in
> theory (except for OS system wide / per-process limits imposed) you should
> be able to mmap up to the full 64 bit address space.
>
> Your virtual memory is unlimited (from "ulimit" output), so that's good.
>
> Mike McCandless
>
> http://blog.mikemccandless.com
>
> On Wed, Sep 7, 2011 at 12:25 PM, Rich Cariens <richcariens@gmail.com>
> wrote:
> > Ahoy ahoy!
> >
> > I've run into the dreaded OOM error with MMapDirectory on a 23G cfs
> > compound index segment file. The stack trace looks pretty much like
> > every other trace I've found when searching for OOM & "map failed"[1].
> > My configuration
> > follows:
> >
> > Solr 1.4.1/Lucene 2.9.3 (plus
> > SOLR-1969<https://issues.apache.org/jira/browse/SOLR-1969>
> > )
> > CentOS 4.9 (Final)
> > Linux 2.6.9-100.ELsmp x86_64 yada yada yada Java SE (build
> > 1.6.0_21-b06) Hotspot 64-bit Server VM (build 17.0-b16, mixed mode)
> > ulimits:
> >    core file size     (blocks, -c)     0
> >    data seg size    (kbytes, -d)     unlimited
> >    file size     (blocks, -f)     unlimited
> >    pending signals    (-i)     1024
> >    max locked memory     (kbytes, -l)     32
> >    max memory size     (kbytes, -m)     unlimited
> >    open files    (-n)     256000
> >    pipe size     (512 bytes, -p)     8
> >    POSIX message queues     (bytes, -q)     819200
> >    stack size    (kbytes, -s)     10240
> >    cpu time    (seconds, -t)     unlimited
> >    max user processes     (-u)     1064959
> >    virtual memory    (kbytes, -v)     unlimited
> >    file locks    (-x)     unlimited
> >
> > Any suggestions?
> >
> > Thanks in advance,
> > Rich
> >
> > [1]
> > ...
> > java.io.IOException: Map failed
> >  at sun.nio.ch.FileChannelImpl.map(Unknown Source)
> >  at
> > org.apache.lucene.store.MMapDirectory$MMapIndexInput.<init>(Unknown
> > Source)
> >  at
> > org.apache.lucene.store.MMapDirectory$MMapIndexInput.<init>(Unknown
> > Source)
> >  at org.apache.lucene.store.MMapDirectory.openInput(Unknown Source)
> >  at org.apache.lucene.index.SegmentReader$CoreReaders.<init>(Unknown
> > Source)
> >
> >  at org.apache.lucene.index.SegmentReader.get(Unknown Source)
> >  at org.apache.lucene.index.SegmentReader.get(Unknown Source)
> >  at org.apache.lucene.index.DirectoryReader.<init>(Unknown Source)
> >  at org.apache.lucene.index.ReadOnlyDirectoryReader.<init>(Unknown
> > Source)
> >  at org.apache.lucene.index.DirectoryReader$1.doBody(Unknown Source)
> >  at org.apache.lucene.index.SegmentInfos$FindSegmentsFile.run(Unknown
> > Source)
> >  at org.apache.lucene.index.DirectoryReader.open(Unknown Source)
> >  at org.apache.lucene.index.IndexReader.open(Unknown Source) ...
> > Caused by: java.lang.OutOfMemoryError: Map failed
> >  at sun.nio.ch.FileChannelImpl.map0(Native Method) ...
> >
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