Messages in this thread Patch in this message | | | Date | Tue, 18 Feb 2020 15:38:01 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH v2 2/5] sched/numa: Replace runnable_load_avg by load_avg |
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On Tue, Feb 18, 2020 at 02:54:14PM +0000, Valentin Schneider wrote: > On 2/14/20 3:27 PM, Vincent Guittot wrote: > > @@ -1473,38 +1473,35 @@ bool should_numa_migrate_memory(struct task_struct *p, struct page * page, > > group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4; > > } > > > > -static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq); > > - > > -static unsigned long cpu_runnable_load(struct rq *rq) > > -{ > > - return cfs_rq_runnable_load_avg(&rq->cfs); > > -} > > +/* > > + * 'numa_type' describes the node at the moment of load balancing. > > + */ > > +enum numa_type { > > + /* The node has spare capacity that can be used to run more tasks. */ > > + node_has_spare = 0, > > + /* > > + * The node is fully used and the tasks don't compete for more CPU > > + * cycles. Nevertheless, some tasks might wait before running. > > + */ > > + node_fully_busy, > > + /* > > + * The node is overloaded and can't provide expected CPU cycles to all > > + * tasks. > > + */ > > + node_overloaded > > +}; > > Could we reuse group_type instead? The definitions are the same modulo > s/group/node/. >
I kept the naming because there is the remote possibility that NUMA balancing will deviate in some fashion. Right now, it's harmless.
> > > > /* Cached statistics for all CPUs within a node */ > > struct numa_stats { > > unsigned long load; > > - > > + unsigned long util; > > /* Total compute capacity of CPUs on a node */ > > unsigned long compute_capacity; > > + unsigned int nr_running; > > + unsigned int weight; > > + enum numa_type node_type; > > }; > > > > -/* > > - * XXX borrowed from update_sg_lb_stats > > - */ > > -static void update_numa_stats(struct numa_stats *ns, int nid) > > -{ > > - int cpu; > > - > > - memset(ns, 0, sizeof(*ns)); > > - for_each_cpu(cpu, cpumask_of_node(nid)) { > > - struct rq *rq = cpu_rq(cpu); > > - > > - ns->load += cpu_runnable_load(rq); > > - ns->compute_capacity += capacity_of(cpu); > > - } > > - > > -} > > - > > struct task_numa_env { > > struct task_struct *p; > > > > @@ -1521,6 +1518,47 @@ struct task_numa_env { > > int best_cpu; > > }; > > > > +static unsigned long cpu_load(struct rq *rq); > > +static unsigned long cpu_util(int cpu); > > + > > +static inline enum > > +numa_type numa_classify(unsigned int imbalance_pct, > > + struct numa_stats *ns) > > +{ > > + if ((ns->nr_running > ns->weight) && > > + ((ns->compute_capacity * 100) < (ns->util * imbalance_pct))) > > + return node_overloaded; > > + > > + if ((ns->nr_running < ns->weight) || > > + ((ns->compute_capacity * 100) > (ns->util * imbalance_pct))) > > + return node_has_spare; > > + > > + return node_fully_busy; > > +} > > + > > As Mel pointed out, this is group_is_overloaded() and group_has_capacity(). > @Mel, you mentioned having a common helper, do you have that laying around? > I haven't seen it in your reconciliation series. >
I didn't merge that part of the first version of my series. I was waiting to see how the implementation for allowing a small degree of imbalance looks like. If it's entirely confined in adjust_numa_balance then I'll create the common helper at the same time. For now, I left the possibility open that numa_classify would use something different than group_is_overloaded or group_has_capacity even if I find that hard to imagine at the moment.
> What I'm naively thinking here is that we could have either move the whole > thing to just sg_lb_stats (AFAICT the fields of numa_stats are a subset of it), > or if we really care about the stack we could tweak the ordering to ensure > we can cast one into the other (not too enticed by that one though). >
Yikes, no I'd rather not do that. Basically all I did before was create a common helper like __lb_has_capacity that only took basic types as parameters. group_has_capacity and numa_has_capacity were simple wrappers that read the correct fields from their respective stats structures.
-- Mel Gorman SUSE Labs
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