On Fri, 2011-08-12 at 13:45 +0800, Wu Fengguang wrote: > Code is > > unsigned long freerun = (thresh + bg_thresh) / 2; > > setpoint = (limit + freerun) / 2; > pos_ratio = abs(dirty - setpoint); > pos_ratio <<= BANDWIDTH_CALC_SHIFT; > do_div(pos_ratio, limit - setpoint + 1); Why do you use do_div()? from the code those things are unsigned long, and you can divide that just fine. Also, there's div64_s64 that can do signed divides for s64 types. That'll loose the extra conditionals you used for abs and putting the sign back. > x = pos_ratio; > pos_ratio = pos_ratio * x >> BANDWIDTH_CALC_SHIFT; > pos_ratio = pos_ratio * x >> BANDWIDTH_CALC_SHIFT; So on 32bit with unsigned long that gets 32=2*(10+b) bits for x, that solves to 6, which isn't going to be enough I figure since (dirty-setpoint) !< 64. So you really need to use u64/s64 types here, unsigned long just won't do, with u64 you have 64=2(10+b) 22 bits for x, which should fit. > if (dirty > setpoint) > pos_ratio = -pos_ratio; > pos_ratio += 1 << BANDWIDTH_CALC_SHIFT; -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
