Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitb4c9c9f

Browse files
vingu-linaroPeter Zijlstra
authored and
Peter Zijlstra
committed
sched/fair: Prefer prev cpu in asymmetric wakeup path
During fast wakeup path, scheduler always check whether local or prevcpus are good candidates for the task before looking for other cpus inthe domain. With commitb7a3316 ("sched/fair: Add asymmetric CPUcapacity wakeup scan") the heterogenous system gains a dedicated pathbut doesn't try to reuse prev cpu whenever possible. If the previouscpu is idle and belong to the LLC domain, we should check it 1stbefore looking for another cpu because it stays one of the bestcandidate and this also stabilizes task placement on the system.This change aligns asymmetric path behavior with symmetric one and reducescases where the task migrates across all cpus of the sd_asym_cpucapacitydomains at wakeup.This change does not impact normal EAS mode but only the overloaded case orwhen EAS is not used.- On hikey960 with performance governor (EAS disable)./perf bench sched pipe -T -l 50000 mainline w/ patch# migrations 999364 0ops/sec 149313(+/-0.28%) 182587(+/- 0.40) +22%- On hikey with performance governor./perf bench sched pipe -T -l 50000 mainline w/ patch# migrations 0 0ops/sec 47721(+/-0.76%) 47899(+/- 0.56) +0.4%According to test on hikey, the patch doesn't impact symmetric systemcompared to current implementation (only tested on arm64)Also read the uclamped value of task's utilization at most twice insteadinstead each time we compare task's utilization with cpu's capacity.Fixes:b7a3316 ("sched/fair: Add asymmetric CPU capacity wakeup scan")Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>Link:https://lkml.kernel.org/r/20201029161824.26389-1-vincent.guittot@linaro.org
1 parent16b0a7a commitb4c9c9f

File tree

1 file changed

+43
-24
lines changed

1 file changed

+43
-24
lines changed

‎kernel/sched/fair.c‎

Lines changed: 43 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -6172,21 +6172,21 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
61726172
staticint
61736173
select_idle_capacity(structtask_struct*p,structsched_domain*sd,inttarget)
61746174
{
6175-
unsigned longbest_cap=0;
6175+
unsigned longtask_util,best_cap=0;
61766176
intcpu,best_cpu=-1;
61776177
structcpumask*cpus;
61786178

6179-
sync_entity_load_avg(&p->se);
6180-
61816179
cpus=this_cpu_cpumask_var_ptr(select_idle_mask);
61826180
cpumask_and(cpus,sched_domain_span(sd),p->cpus_ptr);
61836181

6182+
task_util=uclamp_task_util(p);
6183+
61846184
for_each_cpu_wrap(cpu,cpus,target) {
61856185
unsigned longcpu_cap=capacity_of(cpu);
61866186

61876187
if (!available_idle_cpu(cpu)&& !sched_idle_cpu(cpu))
61886188
continue;
6189-
if (task_fits_capacity(p,cpu_cap))
6189+
if (fits_capacity(task_util,cpu_cap))
61906190
returncpu;
61916191

61926192
if (cpu_cap>best_cap) {
@@ -6198,44 +6198,42 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
61986198
returnbest_cpu;
61996199
}
62006200

6201+
staticinlineboolasym_fits_capacity(inttask_util,intcpu)
6202+
{
6203+
if (static_branch_unlikely(&sched_asym_cpucapacity))
6204+
returnfits_capacity(task_util,capacity_of(cpu));
6205+
6206+
return true;
6207+
}
6208+
62016209
/*
62026210
* Try and locate an idle core/thread in the LLC cache domain.
62036211
*/
62046212
staticintselect_idle_sibling(structtask_struct*p,intprev,inttarget)
62056213
{
62066214
structsched_domain*sd;
6215+
unsigned longtask_util;
62076216
inti,recent_used_cpu;
62086217

62096218
/*
6210-
*For asymmetricCPU capacity systems, our domain of interest is
6211-
*sd_asym_cpucapacity rather than sd_llc.
6219+
*On asymmetricsystem, update task utilization because we will check
6220+
*that the task fits with cpu's capacity.
62126221
*/
62136222
if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6214-
sd=rcu_dereference(per_cpu(sd_asym_cpucapacity,target));
6215-
/*
6216-
* On an asymmetric CPU capacity system where an exclusive
6217-
* cpuset defines a symmetric island (i.e. one unique
6218-
* capacity_orig value through the cpuset), the key will be set
6219-
* but the CPUs within that cpuset will not have a domain with
6220-
* SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6221-
* capacity path.
6222-
*/
6223-
if (!sd)
6224-
gotosymmetric;
6225-
6226-
i=select_idle_capacity(p,sd,target);
6227-
return ((unsigned)i<nr_cpumask_bits) ?i :target;
6223+
sync_entity_load_avg(&p->se);
6224+
task_util=uclamp_task_util(p);
62286225
}
62296226

6230-
symmetric:
6231-
if (available_idle_cpu(target)||sched_idle_cpu(target))
6227+
if ((available_idle_cpu(target)||sched_idle_cpu(target))&&
6228+
asym_fits_capacity(task_util,target))
62326229
returntarget;
62336230

62346231
/*
62356232
* If the previous CPU is cache affine and idle, don't be stupid:
62366233
*/
62376234
if (prev!=target&&cpus_share_cache(prev,target)&&
6238-
(available_idle_cpu(prev)||sched_idle_cpu(prev)))
6235+
(available_idle_cpu(prev)||sched_idle_cpu(prev))&&
6236+
asym_fits_capacity(task_util,prev))
62396237
returnprev;
62406238

62416239
/*
@@ -6258,7 +6256,8 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
62586256
recent_used_cpu!=target&&
62596257
cpus_share_cache(recent_used_cpu,target)&&
62606258
(available_idle_cpu(recent_used_cpu)||sched_idle_cpu(recent_used_cpu))&&
6261-
cpumask_test_cpu(p->recent_used_cpu,p->cpus_ptr)) {
6259+
cpumask_test_cpu(p->recent_used_cpu,p->cpus_ptr)&&
6260+
asym_fits_capacity(task_util,recent_used_cpu)) {
62626261
/*
62636262
* Replace recent_used_cpu with prev as it is a potential
62646263
* candidate for the next wake:
@@ -6267,6 +6266,26 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
62676266
returnrecent_used_cpu;
62686267
}
62696268

6269+
/*
6270+
* For asymmetric CPU capacity systems, our domain of interest is
6271+
* sd_asym_cpucapacity rather than sd_llc.
6272+
*/
6273+
if (static_branch_unlikely(&sched_asym_cpucapacity)) {
6274+
sd=rcu_dereference(per_cpu(sd_asym_cpucapacity,target));
6275+
/*
6276+
* On an asymmetric CPU capacity system where an exclusive
6277+
* cpuset defines a symmetric island (i.e. one unique
6278+
* capacity_orig value through the cpuset), the key will be set
6279+
* but the CPUs within that cpuset will not have a domain with
6280+
* SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
6281+
* capacity path.
6282+
*/
6283+
if (sd) {
6284+
i=select_idle_capacity(p,sd,target);
6285+
return ((unsigned)i<nr_cpumask_bits) ?i :target;
6286+
}
6287+
}
6288+
62706289
sd=rcu_dereference(per_cpu(sd_llc,target));
62716290
if (!sd)
62726291
returntarget;

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp