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include vtd.inc
 
VxDcall VTD_Begin_Min_Int_Period
 
The VTD_Begin_Min_Int_Period service is used by virtual devices to ensure a
minimum accuracy for system timing. When this service is called, if the
interrupt period specified is lower than the current timer interrupt
frequency, the interrupt period will be set to the new frequency.
 
Parameter  Description
────────────────────────────────────────────────────────────────────────────
 
EAX        Specifies the desired interrupt period.
 
Return Value
 
If carry clear, the interrupt period is set. Otherwise, the specified
interrupt period is not valid
 
Comments
 
Until a matching call to the VTD_End_Min_Int_Period service is made, the
timer interrupt frequency is guaranteed to never be slower than the value
specified.
 
A virtual device should call this service only once before calling
VTD_End_Min_Int_Period.
 
Typically the Begin_Min_Int_Period and End_Min_Int_Period services are used
by devices such as execution profilers that need extremely accurate timing.
VMM system time out services rely on the VTD to keep time. Therefore, more
frequent the timer interrupts, will allow the time-out services to be more
accurate.
 
Fast timer interrupt periods can be very, very expensive in terms of total
system performance. For example, on some machines a timer interrupt of 1
millisecond will degrade total machine throughput by 10% and disk I/O by up
to 50%.
 
Uses
 
Flags
 
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