Modify Number of Interrupt Vectors Requested

Use the ddi_intr_set_nreq(9F) function to change the number of interrupt vectors requested.

int
ddi_intr_set_nreq (dev_info_t *dip, int nreq);

When the Interrupt Resource Management feature is available, a driver can use the ddi_intr_set_nreq() function to dynamically adjust the total number of interrupt vectors requested. The driver might do this in response to the actual load that exists once the driver is attached.

A driver must first call ddi_intr_alloc(9F) to request an initial number of interrupt vectors. Any time after the ddi_intr_alloc()call, the driver can call ddi_intr_set_nreq() to change its request size. The specified nreq value is the driver's new total number of requested interrupt vectors. The Interrupt Resource Management feature might rebalance the number of interrupts allocated to each driver in the system in response to this new request. Whenever the Interrupt Resource Management feature rebalances the number of interrupts allocated to drivers, each affected driver receives a callback notification that more or fewer interrupt vectors are available for the driver to use.

A driver might dynamically adjust its total number of requested interrupt vectors if, for example, it uses interrupts in conjunction with specific transactions that it is processing. A storage driver might associate a DMA engine with each ongoing transaction, thus requiring interrupt vectors for that reason. A driver might make calls to ddi_intr_set_nreq() in its open(9F) and close(9F) routines to scale its interrupt usage in response to actual use of the driver.