SetProcessWorkingSetSize
The SetProcessWorkingSetSize
function sets the minimum and maximum working set sizes for a specified
process.
The working set
of a process is the set of memory pages currently visible to the process in
physical RAM memory. These pages are resident and available for an application
to use without triggering a page fault. The size of the working set of a
process is specified in bytes. The minimum and maximum working set sizes affect
the virtual memory paging behavior of a process.
BOOL SetProcessWorkingSetSize(
|
HANDLE hProcess, |
// open handle to
the process of interest |
|
DWORD dwMinimumWorkingSetSize, |
// specifies
minimum working set size |
|
DWORD dwMaximumWorkingSetSize |
// specifies
maximum working set size |
|
); |
|
Parameters
hProcess
An open
handle to the process whose working set sizes will be set.
Windows
NT: The handle must have
PROCESS_SET_QUOTA access rights. For more information, see Process Objects.
dwMinimumWorkingSetSize
Specifies a
minimum working set size for the process. The virtual memory manager attempts
to keep at least this much memory resident in the process whenever the process
is active.
If both dwMinimumWorkingSetSize
and dwMaximumWorkingSetSize have the value 0xffffffff, the function
temporarily trims the working set of the specified process to zero. This
essentially swaps the process out of physical RAM memory.
dwMaximumWorkingSetSize
Specifies a
maximum working set size for the process. The virtual memory manager attempts
to keep no more than this much memory resident in the process whenever the
process is active and memory is in short supply.
If both dwMinimumWorkingSetSize
and dwMaximumWorkingSetSize have the value 0xffffffff, the function
temporarily trims the working set of the specified process to zero. This
essentially swaps the process out of physical RAM memory.
Return Values
If the
function succeeds, the return value is nonzero.
If the
function fails, the return value is zero. Call GetLastError to obtain
extended error information.
Remarks
The working
set of the specified process can be emptied by specifying the value 0xffffffff
for both the minimum and maximum working set sizes.
If the values
of either dwMinimumWorkingSetSize or dwMaximumWorkingSetSize are
greater than the process current working set sizes, the specified process must
have the SE_INC_BASE_PRIORITY_NAME privilege. Users in the Administrators and
Power Users groups generally have this privilege. For more information about
security privileges, see Privileges.
The operating
system allocates working set sizes on a first-come, first-served basis. For
example, if an application successfully sets 40 megabytes as its minimum
working set size on a 64-megabyte system, and a second application requests a
40-megabyte working set size, the operating system denies the second
application s request.
Using the SetProcessWorkingSetSize
function to set an application's minimum and maximum working set sizes does not
guarantee that the requested memory will be reserved, or that it will remain
resident at all times. When the application is idle, or a low-memory situation
causes a demand for memory, the operating system can reduce the application's
working set. An application can use the VirtualLock function to lock
ranges of the application's virtual address space in memory; however, that can
potentially degrade the performance of the system.
When you
increase the working set size of an application, you are taking away physical
memory from the rest of the system. This can degrade the performance of other
applications and the system as a whole. It can also lead to failures of operations
that require physical memory to be present; for example, creating processes,
threads, and kernel pool. Thus, you must use the SetProcessWorkingSetSize
function carefully. You must always consider the performance of the whole
system when you are designing an application.
See Also