Int 31H Function 0602H
Mark Real Mode Region as Pageable
Advises the DPMI host that the specified memory below the 1 MB
boundary may be paged to disk.
AX = 0602H
BX:CX = starting linear address of memory to mark as
SI:DI = size of region to be marked (bytes)
if function successful
Carry flag = clear
if function unsuccessful
Carry flag = set
AX = error code
|8002H||invalid state (region already marked as pageable)|
|8025H||invalid linear address (region is above 1 MB boundary)|
- If the function returns an error, none of the memory has been
marked as pageable.
- If the specified region overlaps part of a page at the beginning
or end of the region, the page(s) will not be marked as pageable.
- Pageability information for a real mode region is maintained as a
binary state, not a count. Therefore, multiple calls to this function
for the same region have no effect.
- For compatibility with DPMI version 0.9 hosts, a client must call
the Relock Real Mode Region function (Int 31H
Function 0603H) to relock the memory region before terminating.
Memory that remains unlocked after the client has terminated could
result in fatal page faults when another program is executed in the
same address space. DPMI 1.0 hosts automatically relock real mode
memory at client termination.
- Under some DPMI hosts, all conventional memory may be locked by
default. If a protected mode program is using memory in the first
megabyte of address space, it is recommended that this function be
used to turn off automatic page locking for regions of memory that
will not be touched at interrupt time.
- The client must not mark memory as pageable in regions that it
does not own; i.e. it may only mark as pageable memory that it has
previously allocated with Int 31H Function
0100H or by a direct call to DOS via the translation functions.
For example, marking all free DOS memory as pageable under some DPMI
hosts could cause a page fault to occur while inside of DOS, resulting
in a crash. Also, a client should not mark the DPMI host data area as
- Note that address space marked as pageable by this function can
still be locked using the Lock Linear Region function (Int 31H Function 0600H). This function is just
an advisory service to allow memory that does not need to be locked to
be paged out; it disables any automatic locking of real mode memory
performed by the DPMI host.
- This function is ignored by DPMI implementations that do not
support virtual memory; the function will return the Carry flag clear
to indicate success, but has no other effect. DPMI hosts which
support virtual memory may also choose to ignore this function, but
such hosts must be able to handle page faults transparently at
arbitrary points during a client's execution, including within
interrupt and exception handlers.