Re: [CFR] Replacing while loops with proper division and multiplication

On 06/05/15 20:31, Neel Natu wrote:
>>> -       runs = 0;
>>> >>-       while (now >= state->nexthard) {
>>> >>-               state->nexthard += tick_sbt;
>>> >>-               runs++;
>>> >>-       }
>>> >>-       if (runs) {
>>> >>+       runs = (now - state->nexthard) / tick_sbt;
>>> >>+       if (runs > 0) {
>>> >>+               printf("R%d ", (int)runs);
>>> >>+               state->nexthard += tick_sbt * runs;
>>> >>                 hct = DPCPU_PTR(hardclocktime);
>>> >>                 *hct = state->nexthard - tick_sbt;
>>> >>                 if (fake < 2) {
> There is a difference in behavior in the two implementations when 'now
> == state->nexthard'. In the loop-based implementation this would end
> up with 'runs = 1' whereas in the division-based implementation it
> would end up with 'runs = 0'.
>
> I am not sure if this is intentional or just an oversight.

Hi Neel,

The nexthard is mainly updated in this piece of code. We can assume that 
"state->nexthard" is aligned to "ticks_sbt". If "state->nexthard % 
ticks_sbt == 0", is that still an issue?

--HPS