Messages in this thread | | | Date | Thu, 9 Dec 2021 15:43:04 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH 2/2] sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs |
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On Thu, Dec 09, 2021 at 02:23:40PM +0000, Valentin Schneider wrote: > On 06/12/21 15:12, Mel Gorman wrote: > > Gautham had similar reasoning to calculate the imbalance at each > > higher-level domain instead of using a static value throughout and > > it does make sense. For each level and splitting the imbalance between > > two domains, this works out as > > > > > > /* > > * Calculate an allowed NUMA imbalance such that LLCs do not get > > * imbalanced. > > */ > > for_each_cpu(i, cpu_map) { > > for (sd = *per_cpu_ptr(d.sd, i); sd; sd = sd->parent) { > > struct sched_domain *child = sd->child; > > > > if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child && > > (child->flags & SD_SHARE_PKG_RESOURCES)) { > > struct sched_domain *top = sd; > > unsigned int llc_sq; > > > > /* > > * nr_llcs = (top->span_weight / llc_weight); > > * imb = (child_weight / nr_llcs) >> 1 > > * > > * is equivalent to > > * > > * imb = (llc_weight^2 / top->span_weight) >> 1 > > * > > */ > > llc_sq = child->span_weight * child->span_weight; > > while (top) { > > top->imb_numa_nr = max(1U, > > (llc_sq / top->span_weight) >> 1); > > top = top->parent; > > } > > > > break; > > } > > } > > } > > > > IIRC Peter suggested punting that logic to before domains get degenerated, > but I don't see how that helps here. If you just want to grab the LLC > domain (aka highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES)) and compare > its span with that of its parents, that can happen after the degeneration, > no? >
I guess we could but I don't see any specific advantage to doing that.
> > I'll test this and should have results tomorrow. > >
The test results indicated that there was still a problem with communicating tasks being pulled apart so am testing a new version.
-- Mel Gorman SUSE Labs
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