This message is sent to all top-level windows when Windows detects that more than 12.5 percent of system time over a 30- to 60-second interval is being spent compacting memory. This indicates that system memory is low.
When an application receives this message, it should free as much memory as possible, taking into account the current level of activity of the application and the total number of applications running in Windows.
wParam
Specifies the ratio of CPU time currently spent by Windows compacting memory. For example, 8000h represents 50% of CPU time.
lParam
This parameter is not used.