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From "luocanrao" <luocan19826...@sohu.com>
Subject 答复: MMapDirectory need twice more virtual memory than actually need?
Date Sat, 30 Jan 2010 11:57:35 GMT
I found this in http://osdir.com/ml/linux-kernel/2009-10/msg03503.html

   If application does mlockall(MCL_FUTURE) it is no longer possible to mmap 
file bigger than main memory or allocate big area of anonymous memory 
in a thread safe manner. Sometimes it is desirable to lock everything 
related to program execution into memory, but still be able to mmap 
big file or allocate huge amount of memory and allow OS to swap them on 
demand. MAP_UNLOCKED allows to do that

  if  mmap method use MAP_UNLOCKED flag, this can expain everything.
  Is that right?

-----邮件原件-----
发件人: Uwe Schindler [mailto:uwe@thetaphi.de] 
发送时间: 2010年1月30日 16:47
收件人: java-user@lucene.apache.org
主题: RE: MMapDirectory need twice more virtual memory than actually need?

MMapDirectory should only be used on 64bit machines with 64bit JVMs. This is described in
the Javadocs.

The additional sizes are caused by reopens and have their reason in specialties with the Java
VM, described in 2.9/3.0 Javadocs of the class, please take a look. You can also enable a
workaround for the missing “unmap” call.

 

-----

Uwe Schindler

H.-H.-Meier-Allee 63, D-28213 Bremen

 <http://www.thetaphi.de/> http://www.thetaphi.de

eMail: uwe@thetaphi.de

 

From: luocanrao [mailto:luocan19826164@sohu.com] 
Sent: Saturday, January 30, 2010 8:31 AM
To: java-user@lucene.apache.org
Subject: MMapDirectory need twice more virtual memory than actually need?

 

Environment: 64 bit linux,memory 8G

When I used pmap instruction to see virtual memory, I found two big anon memory which grows
with the index file size.

I had the two following pictures to show the problem, can you explain?

         This is why I got out of memory exception in 32 bit machine. Because my index file
size is only 800m.

                                                                 Anon memory picture



                                                                 Indexfile memory picture





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