Messages in this thread | | | Date | Fri, 14 Apr 2017 13:38:13 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC 2/3] sched/topology: fix sched groups on NUMA machines with mesh topology |
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On Thu, Apr 13, 2017 at 10:56:08AM -0300, Lauro Ramos Venancio wrote: > This patch constructs the sched groups from each CPU perspective. So, on > a 4 nodes machine with ring topology, while nodes 0 and 2 keep the same > groups as before [(3, 0, 1)(1, 2, 3)], nodes 1 and 3 have new groups > [(0, 1, 2)(2, 3, 0)]. This allows moving tasks between any node 2-hops > apart.
Ah,.. so after drawing pictures I see what went wrong; duh :-(
An equivalent patch would be (if for_each_cpu_wrap() were exposed):
@@ -521,11 +588,11 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu) struct cpumask *covered = sched_domains_tmpmask; struct sd_data *sdd = sd->private; struct sched_domain *sibling; - int i; + int i, wrap;
cpumask_clear(covered);
- for_each_cpu(i, span) { + for_each_cpu_wrap(i, span, cpu, wrap) { struct cpumask *sg_span; if (cpumask_test_cpu(i, covered))
We need to start iterating at @cpu, not start at 0 every time.
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