interrupt latency in mynewt

[WangJiacheng]

Hi,

I have an interrupt triggered  by GPIO input, and observed different interrupt 
latency from different CPU state. If all the tasks are sleep, the interrupt 
latency is about 20us-30us, if the CPU is in idle mode with simple calling 
“__WFI()”, the interrupt latency is about 10us-15us, and if the CPU is running, 
the interrupt latency can be within 8us.

I do the test as following, create a low priority task with 3 case:

1), the task loop is like
while (1){
   /* keep the task in sleep mode, the interrupt will be 20us-30us */
    os_time_delay(OS_TICKS_PER_SEC);
}

2). the task loop is like
while (1){
   /* put the CPU in idle mode by simple calling WFI, the interrupt will be 
10us-150us */
    __WFI;
}

3). the task loop is like
while (1){
   /* keep the CPU always running, the interrupt will be within 8us */
   os_cputime_delay_usecs(1000000);
}

Any idea to reduce the interrupt latency from all tasks are in sleep mode? or 
there is a hard limitation of interrupt response time?

Thanks,

Jiacheng