Windows 7 What's wrong with PAGE_NOCACHE in VirtualAlloc/VirtualFree

[erwin]

Hi, I have this code:

// AllocTest.cpp : Defines the entry point for the console application.
//
#include <windows.h>
#include <stdio.h>

int main(int argc, char * argv[])
{    
  if ( ! SetProcessWorkingSetSize( GetCurrentProcess(), 1024 * 1024 * 1024 * 1.2,  1024 * 1024 * 1024 * 1.2 ) ) {
    return -1;
  }

  void * buffer = VirtualAlloc( NULL,  1024 * 1024 * 1024, MEM_COMMIT, PAGE_READWRITE | [COLOR=Red]PAGE_NOCACHE[/COLOR] );
  memset( buffer, 1,  1024 * 1024 * 1024 );

  getchar();

  VirtualFree( buffer, 0, MEM_RELEASE );

  return 0;
}

On VirtualFree() there is - with the PAGE_NOCACHE option in VirtualAlloc - a heavy cpu-load over more than 10 sec.
Without this option there is only a short peak in the performance graph. But under XP there is no such behaviour.