== privvmpages ==
FIXMEMemory allocation limit. <code>Privvmpages</code> parameterallows controlling the amount of memory allocated by applications. The <code>barrier</code> and the <code>limit</code> of <code>privvmpages</code> parametercontrol the upper boundary of the total size of allocated memory.Note that this upper boundary doesn't guarantee that the Virtual Environmentwill be able to allocate that much memory, neither does it guarantee thatother Virtual Environments will be able to allocate their fair share ofmemory.The primary mechanism to control memory allocation is the <code>[[vmguarpages]]</code>guarantee. <code>Privvmpages</code> parameter accounts allocated (but, possibly,not used yet) memory.The accounted value is an estimation how much memory will be really consumedwhen the Virtual Environment's applications start to use the allocatedmemory.Consumed memory is accounted into <code>[[oomguarpages]]</code> parameter. Since the memory accounted into <code>privvmpages</code> may not be actually used,the sum of current <code>privvmpages</code> values for all Virtual Environmentsmay exceed the RAM and swap size of the computer. There should be a safety gap between the <code>barrier</code> and the <code>limit</code>for <code>privvmpages</code> parameter to reduce the number of memory allocationfailures that the application is unable to handle.This gap will be used for “high-priority” memory allocations, suchas process stack expansion.Normal priority allocations will fail when the <code>barrier</code> if<code>privvmpages</code> is reached. Total <code>privvmpages</code> should match the physical resources of thecomputer.Also, it is important not to allow any Virtual Environment to allocate asignificant portion of all system RAM to avoid serious service leveldegradation for other VEs.Both these configuration requirements are discussed in [[UBC systemwide configuration#Allocated memory]].