On Mon, 2015-02-02 at 11:00 -0800, Linus Torvalds wrote: > Hmm. I don't disagree, but would like some more feedback. > > Davidlohr - you were the person to touch this function last (commit > 30493cc9dddb: "lib/int_sqrt.c: optimize square root algorithm"), and > you did so for performance reasons. And in fact, when you did that, > you removed that initial loop: > > - one = 1UL << (BITS_PER_LONG - 2); > - while (one > op) > - one >>= 2; > > but I'm not sure that was actually all that conscious, I think the > real optimization was the changes inside the loop to make the final > real loop faster and simpler.
I missed that. And yes, the real optimization should be in the loop. > > Also, you had performance numbers, so presumably a test harness for it > all. It probably depends a lot on the actual distribution of argument > values, of course, but it would be good to accompany the patch with > actual real numbers like lasty time. Aha. In my case I recall I ran a usersapce program using each function from 1 to a million, and throwing perf at it for 10 times. > (I'm also not entirely sure what uses int_sqrt() that ends up being so > performance-critical, so it would be good to document that too, since > that probably also matters for the "what's the normal argument range" > question..) It's not a big deal afaik. Thanks, Davidlohr -- 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/
