Hi, On Mon, Jul 06, 2015 at 01:44:30PM +0200, Peter Zijlstra wrote: > On Mon, Jul 06, 2015 at 08:14:37AM +0530, Afzal Mohammed wrote:
> > scaled down weight 'fact' would not be > u32 rather than unlikely as the > > values being passed for delta is either NICE_O_LOAD or the weight of the > > 'se' which would be a value that can be accomodated in a u32. > > This needs a bit more on why se->load.weight must fit u32 (its true, but > not evident from this text). Okay, I will add an equivalent of the below to the log, "se->load.weight can have either the values in prio_to_weight[] for cases where 'se' is a task or capped to MAX_SHARES (1 << 18) when it is a group. And these values can be accomodated in a u32.", and send the patch, unless a negative opinion on the above. > Now as long as we never call __calc_delta() on a rq weight -- which is a > sum of weights and can indeed be larger than u32, we can indeed remove > this. My understanding is that we do not call __calc_delta() on rq weight. > And I think we already assume such, see this story on why shift will > remain positive. ok > > The hunk being removed here > > would not make a difference to it as this is on scaled weight > u32. > > And pre-"9dbdb15553239" doesn't seem to have logical equivalent of hunk > > removed here either. > > -ENOPARSE. Reading 9dbdb15553239 ("sched/fair: Rework sched_fair time accounting") again, realized that I am wrong on this, that was referring to the below statement removed in that commit, if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION))) tmp = (u64)delta_exec * scale_load_down(weight); earlier came to a reasoning that as scale_load_down(weight) was not separately typecasted, value above u32 would be discarded, that non parsable statement meant that weight > u32 was not considered. Since cast has precedence over multiply, that statement of mine was wrong. Regards Afzal -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/