Messages in this thread | | | Date | Sat, 07 Feb 2004 10:41:18 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH] Load balancing problem in 2.6.2-mm1 |
| |
Martin J. Bligh wrote:
>>From a later email .... >> >>Hopefully just tending to round down more would damp it better. >>*imbalance = (*imbalance + SCHED_LOAD_SCALE/2) >> SCHED_LOAD_SHIFT; >>Or even remove the addition all together. >> > >I'd side with just removing the addition alltogether ... > >
By that stage though, it has already passed through the imbalance_pct filter, and with the higher precision and averaging of previous loads, it might take a while to get there.
>>>Moreover, as Rick pointed out, it's particularly futile over idle cpus ;-) >>> >>I don't follow... >> > >If CPU 7 has 1 task, and cpu 8 has 0 tasks, there's an imbalance of 1. >There is no point whatsoever in bouncing that task back and forth >between cpu 7 and 8 - it just makes things slower, and trashes the cache. >There's *no* fairness issue here. > >
Right, it should not be moved. I think Anton is seeing a problem with active balancing, and not so much a problem with the imbalance calculation though.
>If CPU 8 has 2 tasks, and cpu 1 has 1 task, there's an imbalance of 1. >*If* that imbalance persists (and it probably won't, given tasks being >created, destroyed, and blocking for IO), we may want to rotate that >to 1 vs 2, and then back to 2 vs 1, etc. in the interests of fairness, >even though it's slower throughput overall. >
Yes, although as long as it's node local and happens a couple of times a second you should be pretty hard pressed noticing the difference.
- 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/
| |