- Name
-
pio
- Default
-
1
- Minimum
-
0
- Maximum
-
2
- Scope
- per-stack
Control of whether Programmed I/O is used instead of DMA for small packets:
-
0
- no (use DMA) -
1
- use PIO for small packets if available (default)Mode
1
will fall back to DMA if PIO is not currently available. -
2
- use PIO for small packets and fail if PIO is not available.Mode
2
will fail to create the stack if the hardware supports PIO but PIO is not currently available.
On hardware that does not support PIO there is no difference between mode 1
and mode 2
.
In all cases, PIO will only be used for small packets (see EF_PIO_THRESHOLD) and if the VI's transmit queue is currently empty. If these conditions are not met DMA will be used, even in mode 2
.
Note: PIO is currently only available on x86_64 systems.
Note: Mode
2
will not prevent a stack from operating without PIO in the event that PIO allocation is originally successful but then fails after an adapter is rebooted or hotplugged while that stack exists.