On Mon, Jan 29, 2018 at 03:27:09PM -0800, Rohit Jain wrote:
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 26a71eb..ce5ccf8 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5625,6 +5625,11 @@ static unsigned long capacity_orig_of(int cpu) return cpu_rq(cpu)->cpu_capacity_orig; }
+static inline bool full_capacity(int cpu) +{
- return capacity_of(cpu) >= (capacity_orig_of(cpu)*3)/4;
+}
I don't like that name; >.75 != 1.
Maybe invert things and do something like:
static inline bool reduced_capacity(int cpu) { return capacity_of(cpu) < (3*capacity_orig_of(cpu))/4; }
@@ -6110,11 +6116,13 @@ 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) && (capacity_of(cpu) > max_cap)) {
max_cap = capacity_of(cpu);
rcpu = cpu;
}
if (idle_cpu(cpu)) { if (!reduced_capacity(cpu)) return cpu;
if (capacity_cpu(cpu) > max_cap) { max_cap = capacity_cpu(cpu); rcpu = cpu; } }
Would be more consistent, I think.
}
- return -1;
- return rcpu;
}
@@ -6143,6 +6151,8 @@ 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 best_cpu = -1;
- unsigned int best_cap = 0;
Randomly different names for the same thing as in select_idle_smt(). Thinking up two different names for the same thing is more work; be more lazy.
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) @@ -6173,8 +6183,15 @@ 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)) {
if (full_capacity(cpu)) {
best_cpu = cpu;
break;
} else if (capacity_of(cpu) > best_cap) {
best_cap = capacity_of(cpu);
best_cpu = cpu;
}
}
No need for the else. And you'll note you're once again inconsistent with your previous self.
But here I worry about big.little a wee bit. I think we're allowed big and little cores on the same L3 these days, and you can't directly compare capacity between them.
Morten / Dietmar, any comments?
@@ -6193,13 +6210,14 @@ 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) &&
return prev;full_capacity(prev))
split before idle_cpu() for a better balance.