[Users] VE allocating lots of unused virtual memory

[Marcus Better]

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Hi,

I have a problem with a big Java application server running in a VE on an 
x86_64 system with 4 GB of physical RAM and 12 GB of swap. The server needs 
a rather big heap size, so its VM footprint is around 1.5 GB, with RSS of 
0.5 GB. So far so good.

Now occasionally the application spawns a new process using fork() and 
exec(). The fork() momentarily doubles the virtual memory required by the 
appliaction, but this extra memory is never used since the spawned process 
is relatively small. Now the VE often does not have room for double the 
appliaction server's memory, so it doesn't work.

I tried solving the problem by increasing the privvmpages parameter, but 
found that I cannot increase the memory available to the VE beyond 4 GB, 
which is the physical RAM size of the system. Is this correct? What is the 
recommended way to solve the problem?

I'm running Debian's kernel 2.6.26-1-openvz-amd64.

Cheers,

Marcus

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