Messages in this thread Patch in this message | | | Date | Sun, 27 Oct 2002 20:23:09 -0800 | From | "Martin J. Bligh" <> | Subject | Re: [Lse-tech] Re: NUMA scheduler (was: 2.5 merge candidate list 1.5) |
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>> Michael, the way I read the NR_CPUS loop, you walk every cpu >> in the system, and take the best from all of them. In which case >> what's the point of the last_exec_cpu stuff? On the other hand, >> I changed your NR_CPUS to 4 (ie just walk the cpus in that node), >> and it got worse. So perhaps I'm just misreading your code ... >> and it does seem significantly cheaper to execute than Erich's. >> > You are reading it correct. The only thing that the last_exec_cpu > does is to help spread the load across nodes. Without that what was > happening is that node 0 would get completely loaded, then node 1, > etc. With it, in cases where one or more runqueues have the same > length, the one chosen tends to get spread out a bit. Not the > greatest solution, but it helps.
OK. I made a simple boring optimisation to your patch. Shaved almost a second off system time for kernbench, and seems idiotproof to me, shouldn't change anything apart from touching fewer runqueues: if we find a runqueue with nr_running == 0, stop searching ... we ain't going to find anything better ;-)
Kernbench: Elapsed User System CPU 2.5.44-mm4 19.676s 192.794s 42.678s 1197.4% 2.5.44-mm4-hbaum-1 19.746s 189.232s 38.354s 1152.2% 2.5.44-mm4-hbaum-12 19.322s 190.176s 40.354s 1192.6% 2.5.44-mm4-hbaum-12-firstzero 19.292s 189.66s 39.428s 1187.4%
Patch is probably space-eaten, so just whack it in by hand.
--- 2.5.44-mm4-hbaum-12/kernel/sched.c 2002-10-27 19:54:25.000000000 -0800 +++ 2.5.44-mm4-hbaum-12-first_low/kernel/sched.c 2002-10-27 16:42:10.000000000 -0800 @@ -2206,6 +2206,8 @@ if (minload > cpu_rq(cur_cpu)->nr_running) { minload = cpu_rq(cur_cpu)->nr_running; best_cpu = cur_cpu; + if (minload == 0) + break; } if (++cur_cpu >= NR_CPUS) cur_cpu = 0; - 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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