Minor nit: version number missing
On 10/07/2017 06:48 PM, Rohit Jain wrote:
While looking for CPUs to place running tasks on, the scheduler
completely ignores the capacity stolen away by RT/IRQ tasks. This patch
changes that behavior to also take the scaled capacity into account.
Signed-off-by: Rohit Jain <rohit.k.j...@oracle.com>
---
kernel/sched/fair.c | 37 ++++++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index eaede50..5b1f7b9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6004,7 +6004,7 @@ static int select_idle_core(struct task_struct *p, struct
sched_domain *sd, int
for_each_cpu(cpu, cpu_smt_mask(core)) {
cpumask_clear_cpu(cpu, cpus);
- if (!idle_cpu(cpu))
+ if (!idle_cpu(cpu) || !full_capacity(cpu))
Do we need to skip the entire core just because 1st cpu in the core
doesn't have full capacity ?
Let's say that is the only idle core available. It will go and try to
select_idle_cpu() to find the idlest cpu.
Is it worth spending extra time to search an idle cpu with full capacity
when there are idle cores available ?
Regards,
Atish
idle = false;
}
@@ -6025,7 +6025,8 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
*/
static int select_idle_smt(struct task_struct *p, struct sched_domain *sd,
int target)
{
- int cpu;
+ int cpu, backup_cpu = -1;
+ unsigned int backup_cap = 0;
if (!static_branch_likely(&sched_smt_present))
return -1;
@@ -6033,11 +6034,17 @@ static int select_idle_smt(struct task_struct *p,
struct sched_domain *sd, int t
for_each_cpu(cpu, cpu_smt_mask(target)) {
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
continue;
- if (idle_cpu(cpu))
- return cpu;
+ if (idle_cpu(cpu)) {
+ if (full_capacity(cpu))
+ return cpu;
+ if (capacity_of(cpu) > backup_cap) {
+ backup_cap = capacity_of(cpu);
+ backup_cpu = cpu;
+ }
+ }
}
- return -1;
+ return backup_cpu;
}
#else /* CONFIG_SCHED_SMT */
@@ -6066,6 +6073,8 @@ static int select_idle_cpu(struct task_struct *p, struct
sched_domain *sd, int t
u64 time, cost;
s64 delta;
int cpu, nr = INT_MAX;
+ int backup_cpu = -1;
+ unsigned int backup_cap = 0;
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
if (!this_sd)
@@ -6096,10 +6105,19 @@ static int select_idle_cpu(struct task_struct *p,
struct sched_domain *sd, int t
return -1;
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
continue;
- if (idle_cpu(cpu))
- break;
+ if (idle_cpu(cpu)) {
+ if (full_capacity(cpu)) {
+ backup_cpu = -1;
+ break;
+ } else if (capacity_of(cpu) > backup_cap) {
+ backup_cap = capacity_of(cpu);
+ backup_cpu = cpu;
+ }
+ }
}
+ if (backup_cpu >= 0)
+ cpu = backup_cpu;
time = local_clock() - time;
cost = this_sd->avg_scan_cost;
delta = (s64)(time - cost) / 8;
@@ -6116,13 +6134,14 @@ static int select_idle_sibling(struct task_struct *p,
int prev, int target)
struct sched_domain *sd;
int i;
- if (idle_cpu(target))
+ if (idle_cpu(target) && full_capacity(target))
return target;
/*
* If the previous cpu is cache affine and idle, don't be stupid.
*/
- if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
+ if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev)
+ && full_capacity(prev))
return prev;
sd = rcu_dereference(per_cpu(sd_llc, target));
