Currently, update_top_cache_domain() is called whenever schedule domain is built or destroyed. But, the following
callpath shows that they're at the same callpath and can be avoided update_top_cache_domain() while destroying schedule
domain and update only at the times of building schedule domains.
partition_sched_domains()
detach_destroy_domain()
cpu_attach_domain()
update_top_cache_domain()
build_sched_domains()
cpu_attach_domain()
update_top_cache_domain()
Signed-off-by: Rakib Mullick <[email protected]>
---
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7c32cb..8c6fee4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5102,8 +5102,8 @@ static void update_top_cache_domain(int cpu)
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
-static void
-cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
+static void cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd,
+ int cpu, bool update_cache_domain)
{
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
@@ -5138,7 +5138,8 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
rcu_assign_pointer(rq->sd, sd);
destroy_sched_domains(tmp, cpu);
- update_top_cache_domain(cpu);
+ if (update_cache_domain)
+ update_top_cache_domain(cpu);
}
/* cpus with isolated domains */
@@ -6021,7 +6022,7 @@ static int build_sched_domains(const struct cpumask *cpu_map,
rcu_read_lock();
for_each_cpu(i, cpu_map) {
sd = *per_cpu_ptr(d.sd, i);
- cpu_attach_domain(sd, d.rd, i);
+ cpu_attach_domain(sd, d.rd, i, 1);
}
rcu_read_unlock();
@@ -6109,7 +6110,7 @@ static void detach_destroy_domains(const struct cpumask *cpu_map)
rcu_read_lock();
for_each_cpu(i, cpu_map)
- cpu_attach_domain(NULL, &def_root_domain, i);
+ cpu_attach_domain(NULL, &def_root_domain, i, 0);
rcu_read_unlock();
}
On Tue, Jul 23, 2013 at 09:44:17PM +0600, Rakib Mullick wrote:
> Currently, update_top_cache_domain() is called whenever schedule domain is built or destroyed. But, the following
> callpath shows that they're at the same callpath and can be avoided update_top_cache_domain() while destroying schedule
> domain and update only at the times of building schedule domains.
>
> partition_sched_domains()
> detach_destroy_domain()
> cpu_attach_domain()
> update_top_cache_domain()
> build_sched_domains()
> cpu_attach_domain()
> update_top_cache_domain()
>
Does it really matter?
>
> Signed-off-by: Rakib Mullick <[email protected]>
> ---
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b7c32cb..8c6fee4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5102,8 +5102,8 @@ static void update_top_cache_domain(int cpu)
> * Attach the domain 'sd' to 'cpu' as its base domain. Callers must
> * hold the hotplug lock.
> */
> -static void
> -cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
> +static void cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd,
> + int cpu, bool update_cache_domain)
> {
> struct rq *rq = cpu_rq(cpu);
> struct sched_domain *tmp;
> @@ -5138,7 +5138,8 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
> rcu_assign_pointer(rq->sd, sd);
> destroy_sched_domains(tmp, cpu);
>
> - update_top_cache_domain(cpu);
> + if (update_cache_domain)
> + update_top_cache_domain(cpu);
> }
>
> /* cpus with isolated domains */
> @@ -6021,7 +6022,7 @@ static int build_sched_domains(const struct cpumask *cpu_map,
> rcu_read_lock();
> for_each_cpu(i, cpu_map) {
> sd = *per_cpu_ptr(d.sd, i);
> - cpu_attach_domain(sd, d.rd, i);
> + cpu_attach_domain(sd, d.rd, i, 1);
> }
> rcu_read_unlock();
>
> @@ -6109,7 +6110,7 @@ static void detach_destroy_domains(const struct cpumask *cpu_map)
>
> rcu_read_lock();
> for_each_cpu(i, cpu_map)
> - cpu_attach_domain(NULL, &def_root_domain, i);
> + cpu_attach_domain(NULL, &def_root_domain, i, 0);
> rcu_read_unlock();
> }
This just makes the code uglier for no gain afaict.
If you really need to do this, key off @sd == NULL or something.
On Tue, Jul 23, 2013 at 9:47 PM, Peter Zijlstra <[email protected]> wrote:
> On Tue, Jul 23, 2013 at 09:44:17PM +0600, Rakib Mullick wrote:
>> Currently, update_top_cache_domain() is called whenever schedule domain is built or destroyed. But, the following
>> callpath shows that they're at the same callpath and can be avoided update_top_cache_domain() while destroying schedule
>> domain and update only at the times of building schedule domains.
>>
>> partition_sched_domains()
>> detach_destroy_domain()
>> cpu_attach_domain()
>> update_top_cache_domain()
>> build_sched_domains()
>> cpu_attach_domain()
>> update_top_cache_domain()
>>
>
> Does it really matter?
Why should we do it twice? More importantly at the time of destroying
even though we know it'll be built again just few moment later.
>
>
> This just makes the code uglier for no gain afaict.
>
> If you really need to do this, key off @sd == NULL or something.
Sorry, would you please a bit more clearer? I can't pick what you're suggesting.
On Tue, Jul 23, 2013 at 10:09 PM, Rakib Mullick <[email protected]> wrote:
> On Tue, Jul 23, 2013 at 9:47 PM, Peter Zijlstra <[email protected]> wrote:
>> On Tue, Jul 23, 2013 at 09:44:17PM +0600, Rakib Mullick wrote:
>>> Currently, update_top_cache_domain() is called whenever schedule domain is built or destroyed. But, the following
>>> callpath shows that they're at the same callpath and can be avoided update_top_cache_domain() while destroying schedule
>>> domain and update only at the times of building schedule domains.
>>>
>>> partition_sched_domains()
>>> detach_destroy_domain()
>>> cpu_attach_domain()
>>> update_top_cache_domain()
>>> build_sched_domains()
>>> cpu_attach_domain()
>>> update_top_cache_domain()
>>>
>>
>> Does it really matter?
>
> Why should we do it twice? More importantly at the time of destroying
> even though we know it'll be built again just few moment later.
>
>>
>>
>> This just makes the code uglier for no gain afaict.
>>
>> If you really need to do this, key off @sd == NULL or something.
>
> Sorry, would you please a bit more clearer? I can't pick what you're suggesting.
You mean using sd == NULL rather than using update_cache_domain variable ?
On Tue, Jul 23, 2013 at 10:20:20PM +0600, Rakib Mullick wrote:
> You mean using sd == NULL rather than using update_cache_domain variable ?
Yes, note how:
@@ -6109,7 +6110,7 @@ static void detach_destroy_domains(const struct cpumask *cpu_map)
rcu_read_lock();
for_each_cpu(i, cpu_map)
- cpu_attach_domain(NULL, &def_root_domain, i);
rcu_read_unlock();
}
Always has NULL for sd? Which means you can do:
@@ -5138,7 +5138,8 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
rcu_assign_pointer(rq->sd, sd);
destroy_sched_domains(tmp, cpu);
- update_top_cache_domain(cpu);
+ if (sd)
+ update_top_cache_domain(cpu);
}
/* cpus with isolated domains */
On Tue, Jul 23, 2013 at 10:53 PM, Peter Zijlstra <[email protected]> wrote:
> On Tue, Jul 23, 2013 at 10:20:20PM +0600, Rakib Mullick wrote:
>
>> You mean using sd == NULL rather than using update_cache_domain variable ?
>
> Yes, note how:
>
> @@ -6109,7 +6110,7 @@ static void detach_destroy_domains(const struct cpumask *cpu_map)
>
> rcu_read_lock();
> for_each_cpu(i, cpu_map)
> - cpu_attach_domain(NULL, &def_root_domain, i);
> rcu_read_unlock();
> }
>
> Always has NULL for sd? Which means you can do:
>
> @@ -5138,7 +5138,8 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
> rcu_assign_pointer(rq->sd, sd);
> destroy_sched_domains(tmp, cpu);
>
> - update_top_cache_domain(cpu);
> + if (sd)
> + update_top_cache_domain(cpu);
> }
>
> /* cpus with isolated domains */
Okay, got it. Will submit an updated patch!
Thanks
Rakib.