Messages in this thread Patch in this message | | | From | subhra mazumdar <> | Subject | [PATCH 1/5] sched: limit cpu search in select_idle_cpu | Date | Thu, 28 Jun 2018 15:44:52 -0700 |
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Put upper and lower limit on cpu search of select_idle_cpu. The lower limit is amount of cpus in a core while upper limit is twice that. This ensures for any architecture we will usually search beyond a core. The upper limit also helps in keeping the search cost low and constant.
Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com> --- kernel/sched/fair.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e497c05..7243146 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6372,7 +6372,7 @@ 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, limit, floor, nr = INT_MAX; this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) @@ -6390,10 +6390,17 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t if (sched_feat(SIS_PROP)) { u64 span_avg = sd->span_weight * avg_idle; - if (span_avg > 4*avg_cost) + floor = cpumask_weight(topology_sibling_cpumask(target)); + if (floor < 2) + floor = 2; + limit = 2*floor; + if (span_avg > floor*avg_cost) { nr = div_u64(span_avg, avg_cost); - else - nr = 4; + if (nr > limit) + nr = limit; + } else { + nr = floor; + } } time = local_clock(); -- 2.9.3
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