Synnefo » snf-ganeti

try:

  import ctypes

except ImportError:

  ctypes = None

# Flags for mlockall() (from bits/mman.h)

_MCL_CURRENT = 1

_MCL_FUTURE = 2

def Mlockall():

  """Lock current process' virtual address space into RAM.

  This is equivalent to the C call mlockall(MCL_CURRENT|MCL_FUTURE),

  see mlock(2) for more details. This function requires ctypes module.

  """

  if ctypes is None:

    logging.warning("Cannot set memory lock, ctypes module not found")

    return

  libc = ctypes.cdll.LoadLibrary("libc.so.6")

  if libc is None:

    logging.error("Cannot set memory lock, ctypes cannot load libc")

    return

  # Some older version of the ctypes module don't have built-in functionality

  # to access the errno global variable, where function error codes are stored.

  # By declaring this variable as a pointer to an integer we can then access

  # its value correctly, should the mlockall call fail, in order to see what

  # the actual error code was.

  libc.__errno_location.restype = ctypes.POINTER(ctypes.c_int)

  if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE):

    logging.error("Cannot set memory lock: %s" %

                  os.strerror(libc.__errno_location().contents.value))

    return

  logging.debug("Memory lock set")