SLEEP or busy-waiting. Which would service an interrupt faster?

Question

I'm programming a PIC microcontroller to service two events via interrupts on a very time constrained environment.

PIC microcontrollers allow a SLEEP mode which wakes the PCU on any external interrupt (INTn) but has a wake delay depending on the selected oscillator mode.

I want to know which option would start servicing the interrupts faster. A main loop like this:

//CPU never goes to sleep, keeps executing a jump
void main(){
    while(1){}
}

or a main loop like this:

//CPU goes to sleep (idle), waits for INTn interrupts.
void main(){
    while(1){
     asm SLEEP;
    }
}

Waking from idle sleep seems to take 2 cycles according to the PIC18F4XK22 whereas a jump instruction (of an infinite while loop may take longer and may or may not be interruptible halfway into the execution of the jump.

Answer 1

You said it yourself, waking up from sleep incurs some delay, depending on the oscillator. The delay will be relatively small for R-C oscillators, and much longer for crystal oscillators.

The second method uses less power, assuming you can sleep for long enough on average for the reduced current to be meaningful.