On 8/30/19 11:19 PM, subhra mazumdar wrote: > Put upper and lower limit on CPU search in select_idle_cpu. The lower limit > is set to amount of CPUs in a core while upper limit is derived from the > latency-nice of the thread. This ensures for any architecture we will > usually search beyond a core. Changing the latency-nice value by user will > change the search cost making it appropriate for given workload. > > Signed-off-by: subhra mazumdar <[email protected]> > --- > kernel/sched/fair.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index b08d00c..c31082d 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6188,7 +6188,7 @@ static int select_idle_cpu(struct task_struct *p, > struct sched_domain *sd, int t > u64 avg_cost, avg_idle; > u64 time, cost; > s64 delta; > - int cpu, nr = INT_MAX; > + int cpu, floor, nr = INT_MAX; > > this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); > if (!this_sd) > @@ -6205,11 +6205,12 @@ static int select_idle_cpu(struct task_struct *p, > struct sched_domain *sd, int t > return -1; > > if (sched_feat(SIS_PROP)) { > - u64 span_avg = sd->span_weight * avg_idle; > - if (span_avg > 4*avg_cost) > - nr = div_u64(span_avg, avg_cost); > - else > - nr = 4; > + floor = cpumask_weight(topology_sibling_cpumask(target)); > + if (floor < 2) > + floor = 2; > + nr = (p->latency_nice * sd->span_weight) / LATENCY_NICE_MAX; I see you defined LATENCY_NICE_MAX = 100, So is the value 100 an experimental value? I was hoping to be something in the power of 2 resulting in just ">>>" rather than the heavy division operation. > + if (nr < floor) > + nr = floor; > } > > time = local_clock(); >
