On Fri, May 30, 2014 at 02:36:06PM +0800, Yuyang Du wrote: > Currently, CPU CC is per CPU. To consolidate, the formula is based on a > heuristic. > Suppose we have 2 CPUs, their task concurrency over time is ('-' means no > task, 'x' having tasks): > > 1) > CPU0: ---xxxx---------- (CC[0]) > CPU1: ---------xxxx---- (CC[1]) > > 2) > CPU0: ---xxxx---------- (CC[0]) > CPU1: ---xxxx---------- (CC[1]) > > If we consolidate CPU0 and CPU1, the consolidated CC will be: CC' = CC[0] + > CC[1] for case 1 and CC'' = (CC[0] + CC[1]) * 2 for case 2. For the cases in > between case 1 and 2 in terms of how xxx overlaps, the CC should be between > CC' and CC''. So, we uniformly use this condition for consolidation (suppose > we consolidate m CPUs to n CPUs, m > n): > > (CC[0] + CC[1] + ... + CC[m-2] + CC[m-1]) * (n + log(m-n)) >=<? (1 * n) * n * > consolidating_coefficient > > The consolidating_coefficient could be like 100% or more or less. >
I'm still struggling to match that to the code presented. > +/* > + * as of now, we have the following assumption > + * 1) every sched_group has the same weight > + * 2) every CPU has the same computing power > + */ Those are complete non starters. > +/* > + * wc_nonshielded_mask - return the nonshielded cpus in the @mask, > + * which is unmasked by the shielded cpus > + * > + * traverse downward the sched_domain tree when the sched_domain contains > + * flag SD_WORKLOAD_CONSOLIDATION, each sd may have more than two groups WTF is a shielded/nonshielded cpu? > +static int cpu_task_hot(struct task_struct *p, u64 now) > +{ > + s64 delta; > + > + if (p->sched_class != &fair_sched_class) > + return 0; > + > + if (unlikely(p->policy == SCHED_IDLE)) > + return 0; > + > + if (wc_push_hot_task) > + return 0; > + > + /* > + * Buddy candidates are cache hot: > + */ > + if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running && > + (&p->se == cfs_rq_of(&p->se)->next || > + &p->se == cfs_rq_of(&p->se)->last)) > + return 1; > + > + if (sysctl_sched_migration_cost == -1) > + return 1; > + if (sysctl_sched_migration_cost == 0) > + return 0; > + > + delta = now - p->se.exec_start; > + > + return delta < (s64)sysctl_sched_migration_cost; > +} In what universe to we need an exact copy of task_hot() ? and on and on it goes.. :-(
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