From: subhra mazumdar <subhra.mazumdar@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@redhat.com,
steven.sistare@oracle.com, dhaval.giani@oracle.com,
rohit.k.jain@oracle.com, daniel.lezcano@linaro.org
Subject: [PATCH 1/5] sched: limit cpu search in select_idle_cpu
Date: Tue, 12 Jun 2018 10:49:58 -0700 [thread overview]
Message-ID: <20180612175002.31453-2-subhra.mazumdar@oracle.com> (raw)
In-Reply-To: <20180612175002.31453-1-subhra.mazumdar@oracle.com>
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..9a6d28d 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)
@@ -6389,11 +6389,18 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
return -1;
if (sched_feat(SIS_PROP)) {
+ floor = cpumask_weight(topology_sibling_cpumask(target));
+ if (floor < 2)
+ floor = 2;
+ limit = 2*floor;
u64 span_avg = sd->span_weight * avg_idle;
- if (span_avg > 4*avg_cost)
+ 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
next prev parent reply other threads:[~2018-06-12 17:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-12 17:49 [RFC/RFT V2 PATCH 0/5] Improve scheduler scalability for fast path subhra mazumdar
2018-06-12 17:49 ` subhra mazumdar [this message]
2018-06-12 20:33 ` [PATCH 1/5] sched: limit cpu search in select_idle_cpu kbuild test robot
2018-06-12 22:12 ` Subhra Mazumdar
2018-06-20 7:32 ` [lkp-robot] [sched] 8dd662615c: reaim.jobs_per_min -3.3% regression kernel test robot
2018-06-12 17:49 ` [PATCH 2/5] sched: introduce per-cpu var next_cpu to track search limit subhra mazumdar
2018-06-12 17:50 ` [PATCH 3/5] sched: rotate the cpu search window for better spread subhra mazumdar
2018-06-12 17:50 ` [PATCH 4/5] sched: add sched feature to disable idle core search subhra mazumdar
2018-06-12 17:50 ` [PATCH 5/5] sched: SIS_CORE " subhra mazumdar
2018-06-28 22:44 [RESEND RFC/RFT V2 PATCH 0/5] Improve scheduler scalability for fast path subhra mazumdar
2018-06-28 22:44 ` [PATCH 1/5] sched: limit cpu search in select_idle_cpu subhra mazumdar
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