we have a xilinx fpga on a pci card.
fpga have some functionals and create every millisec. a interrupt.
on the fpga there is a SRAM.
normal the jitter on there irq is less than 5µs.
On a dual core system we have very have interrupt latency ( > 100µs] , while one core write many data to sram.
we use a fujitsu D3071-S board with intel Q67 chipset.
We don't found anything, how we can reduce the latency.
Interrupt latency depends on various factors.
The processor may be busy with another interrupt which is having higher priority and might be occuring very frequenly and processor schedulkes cpu to service it.
Check in that aspect.