[OpenSHORE-devel] Running OpenSHORE 2.0.0 Alpha 2 Server on Linux 2.6.x

[Helge S. <Hel...@gm...>]

Hello SHORE'ler,

an OpenSHORE 2.0.0 Alpha 2 server running on Linux 2.6.x reports a "no 
more memory" error while importing several long documents. This error is 
caused by changes in the kernel memory address space allocation strategy 
of the "mmap" system call. Linux 2.6.x kernels allocate by default address 
space for file mappings from high to low addresses instead from a fixed 
address behind the program code to high addresses (as all 2.x kernels 
before). Because of this, existing mappings can not be extended any more 
to build a larger continuous address spaces. So OpenSHORE 2.0.0 Alpha 2 
reports an out of memory error first time when trying to extend his 
database file.

As a workaround you can switch back Linux 2.6.x to his old behaviour by 
the command (as root):

sysctl -w vm.legacy_va_layout=1

After calling this command an OpenSHORE should work as on older kernels. 
The command changes also the "mmap" start address, so that old database 
files can not be read any more and should be deleted. Unfortunately these 
options is global and can not be adjusted per process, so that all (new) 
started programs are switched backed to the old virtual address space 
layout.

You can set this option at system start up by adding the line

vm.legacy_va_layout=1

to the file /etc/sysctl.conf. If your Linux system has no sysctl 
program/package installed, you can also add the simple command

echo 1 > /proc/sys/vm/legacy_va_layout

to your start up scripts.

The next OpenSHORE version (Alpha 3 or Beta 1) will fix this problem by 
choosing a "mmap" start address by hand. If you have time, you can extend 
source file src/misc/os/osUnix/FileMapperUnix.cpp by your self and send me 
your suggestions for choosing a starting address.

I filed a bug report in the OpenSHORE SourceForge trackers under

http://sourceforge.net/tracker/index.php?func=detail&aid=1100480&group_id=65882&atid=512595

I will close this report, if the problem is solved.

Best regards, Helge

-- 
Helge Schulz	http://www.openshore.org