Messages in this thread | | | Date | Tue, 27 Aug 2002 11:35:49 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] sched.c |
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Lahti Oy wrote: > > Small patch that makes NR_CPUS loops decrement from 31 to 0 in sched.c to > squeeze out some cycles (of course only on SMP machines). Also deprecated a > macro that was only used once in the code and changed one if-conditional to > else if. > > ... > > - for (i = 0; i < NR_CPUS; i++) > + for (i = NR_CPUS; i; i--) > sum += cpu_rq(i)->nr_running;
Off-by-one there. You'd want
for (i = NR_CPUS; --i >= 0; )
or something similarly foul ;)
But these are not performance-critical functions. And by far the most inefficient part of them is that they're reading data for CPUs which cannot exist. That can be fixed with a `cpu_possible(i)' test in there, but Rusty was going to give us a `for_each_cpu' macro. We haven't seen that yet. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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