diff mbox series

[v3,2/2] sched/topology: Sort asym_cap_list in descending order

Message ID 20231231175218.510721-3-qyousef@layalina.io
State New
Headers
Series sched: Don't trigger misfit if affinity is restricted |

Commit Message

Qais Yousef Dec. 31, 2023, 5:52 p.m. UTC 
  So that searches always start from biggest CPU which would help misfit
detection logic to be more efficient.

I see the following when adding trace_printks() during add and del
operations

            init-1       [000] .....     0.058128: asym_cpu_capacity_update_data: Added new capacity 250. Capacity list order:
            init-1       [000] .....     0.058132: asym_cpu_capacity_update_data: -- 250
            init-1       [000] .....     0.058135: asym_cpu_capacity_update_data: Added new capacity 620. Capacity list order:
            init-1       [000] .....     0.058136: asym_cpu_capacity_update_data: -- 620
            init-1       [000] .....     0.058137: asym_cpu_capacity_update_data: -- 250
            init-1       [000] .....     0.058139: asym_cpu_capacity_update_data: Added new capacity 1024. Capacity list order:
            init-1       [000] .....     0.058140: asym_cpu_capacity_update_data: -- 1024
            init-1       [000] .....     0.058141: asym_cpu_capacity_update_data: -- 620
            init-1       [000] .....     0.058142: asym_cpu_capacity_update_data: -- 250
            init-1       [000] .....     0.058143: asym_cpu_capacity_scan: Final capacity list order:
            init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 1024
            init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 620
            init-1       [000] .....     0.058146: asym_cpu_capacity_scan: -- 250
           <...>-244     [007] .....     1.959174: asym_cpu_capacity_update_data: Added new capacity 160. Capacity list order:
           <...>-244     [007] .....     1.959175: asym_cpu_capacity_update_data: -- 1024
           <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 620
           <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 250
           <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 160
           <...>-244     [007] .....     1.959183: asym_cpu_capacity_update_data: Added new capacity 498. Capacity list order:
           <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 1024
           <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 620
           <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 498
           <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 250
           <...>-244     [007] .....     1.959186: asym_cpu_capacity_update_data: -- 160
           <...>-244     [007] .....     1.959204: asym_cpu_capacity_scan: Deleted capacity 620
           <...>-244     [007] .....     1.959208: asym_cpu_capacity_scan: Deleted capacity 250
           <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: Final capacity list order:
           <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: -- 1024
           <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 498
           <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 160
         rcuop/7-66      [001] b....     1.968114: free_asym_cap_entry: Freeing capacity 620
         rcuop/7-66      [001] b....     1.968118: free_asym_cap_entry: Freeing capacity 250

Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
---
 kernel/sched/topology.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

Comments

Pierre Gondois Jan. 2, 2024, 5:09 p.m. UTC | #1 
Hello Qais,
I just have some comments regarding the commit message/comments,
otherwise the code (of the 2 patches) looks good to me,

Regards,
Pierre

On 12/31/23 18:52, Qais Yousef wrote:
> So that searches always start from biggest CPU which would help misfit
> detection logic to be more efficient.
> 
> I see the following when adding trace_printks() during add and del
> operations
> 
>              init-1       [000] .....     0.058128: asym_cpu_capacity_update_data: Added new capacity 250. Capacity list order:
>              init-1       [000] .....     0.058132: asym_cpu_capacity_update_data: -- 250
>              init-1       [000] .....     0.058135: asym_cpu_capacity_update_data: Added new capacity 620. Capacity list order:
>              init-1       [000] .....     0.058136: asym_cpu_capacity_update_data: -- 620
>              init-1       [000] .....     0.058137: asym_cpu_capacity_update_data: -- 250
>              init-1       [000] .....     0.058139: asym_cpu_capacity_update_data: Added new capacity 1024. Capacity list order:
>              init-1       [000] .....     0.058140: asym_cpu_capacity_update_data: -- 1024
>              init-1       [000] .....     0.058141: asym_cpu_capacity_update_data: -- 620
>              init-1       [000] .....     0.058142: asym_cpu_capacity_update_data: -- 250
>              init-1       [000] .....     0.058143: asym_cpu_capacity_scan: Final capacity list order:
>              init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 1024
>              init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 620
>              init-1       [000] .....     0.058146: asym_cpu_capacity_scan: -- 250
>             <...>-244     [007] .....     1.959174: asym_cpu_capacity_update_data: Added new capacity 160. Capacity list order:
>             <...>-244     [007] .....     1.959175: asym_cpu_capacity_update_data: -- 1024
>             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 620
>             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 250
>             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 160
>             <...>-244     [007] .....     1.959183: asym_cpu_capacity_update_data: Added new capacity 498. Capacity list order:
>             <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 1024
>             <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 620
>             <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 498
>             <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 250
>             <...>-244     [007] .....     1.959186: asym_cpu_capacity_update_data: -- 160
>             <...>-244     [007] .....     1.959204: asym_cpu_capacity_scan: Deleted capacity 620
>             <...>-244     [007] .....     1.959208: asym_cpu_capacity_scan: Deleted capacity 250
>             <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: Final capacity list order:
>             <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: -- 1024
>             <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 498
>             <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 160
>           rcuop/7-66      [001] b....     1.968114: free_asym_cap_entry: Freeing capacity 620
>           rcuop/7-66      [001] b....     1.968118: free_asym_cap_entry: Freeing capacity 250

IMO the trace is not necessary.

> 
> Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
> Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
> ---
>   kernel/sched/topology.c | 16 ++++++++++++++--
>   1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index ba4a0b18ae25..1505677e4247 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1384,18 +1384,30 @@ static void free_asym_cap_entry(struct rcu_head *head)
>   static inline void asym_cpu_capacity_update_data(int cpu)
>   {
>   	unsigned long capacity = arch_scale_cpu_capacity(cpu);
> -	struct asym_cap_data *entry = NULL;
> +	struct asym_cap_data *insert_entry = NULL;
> +	struct asym_cap_data *entry;
>   
> +	/*
> +	 * Search if capacity already exits. If not, track which the entry
> +	 * where we should insert to keep the list ordered descendingly.
> +	 */

IMO just a small comment like the one suggested below should be enough,
but this is just a suggestion.

>   	list_for_each_entry(entry, &asym_cap_list, link) {
>   		if (capacity == entry->capacity)
>   			goto done;
> +		else if (!insert_entry && capacity > entry->capacity)
> +			insert_entry = list_prev_entry(entry, link);
>   	}
>   
>   	entry = kzalloc(sizeof(*entry) + cpumask_size(), GFP_KERNEL);
>   	if (WARN_ONCE(!entry, "Failed to allocate memory for asymmetry data\n"))
>   		return;
>   	entry->capacity = capacity;
> -	list_add_rcu(&entry->link, &asym_cap_list);
> +
> +	/* If NULL then the new capacity is the smallest, add last. */

(something like):
	/* asym_cap_list is sorted by descending order. */
> +	if (!insert_entry)
> +		list_add_tail_rcu(&entry->link, &asym_cap_list);
> +	else
> +		list_add_rcu(&entry->link, &insert_entry->link);
>   done:
>   	__cpumask_set_cpu(cpu, cpu_capacity_span(entry));
>   }
Qais Yousef Jan. 4, 2024, 7:17 p.m. UTC | #2 
On 01/02/24 18:09, Pierre Gondois wrote:
> Hello Qais,
> I just have some comments regarding the commit message/comments,
> otherwise the code (of the 2 patches) looks good to me,

Thanks for taking a look!

> 
> On 12/31/23 18:52, Qais Yousef wrote:
> > So that searches always start from biggest CPU which would help misfit
> > detection logic to be more efficient.
> > 
> > I see the following when adding trace_printks() during add and del
> > operations
> > 
> >              init-1       [000] .....     0.058128: asym_cpu_capacity_update_data: Added new capacity 250. Capacity list order:
> >              init-1       [000] .....     0.058132: asym_cpu_capacity_update_data: -- 250
> >              init-1       [000] .....     0.058135: asym_cpu_capacity_update_data: Added new capacity 620. Capacity list order:
> >              init-1       [000] .....     0.058136: asym_cpu_capacity_update_data: -- 620
> >              init-1       [000] .....     0.058137: asym_cpu_capacity_update_data: -- 250
> >              init-1       [000] .....     0.058139: asym_cpu_capacity_update_data: Added new capacity 1024. Capacity list order:
> >              init-1       [000] .....     0.058140: asym_cpu_capacity_update_data: -- 1024
> >              init-1       [000] .....     0.058141: asym_cpu_capacity_update_data: -- 620
> >              init-1       [000] .....     0.058142: asym_cpu_capacity_update_data: -- 250
> >              init-1       [000] .....     0.058143: asym_cpu_capacity_scan: Final capacity list order:
> >              init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 1024
> >              init-1       [000] .....     0.058145: asym_cpu_capacity_scan: -- 620
> >              init-1       [000] .....     0.058146: asym_cpu_capacity_scan: -- 250
> >             <...>-244     [007] .....     1.959174: asym_cpu_capacity_update_data: Added new capacity 160. Capacity list order:
> >             <...>-244     [007] .....     1.959175: asym_cpu_capacity_update_data: -- 1024
> >             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 620
> >             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 250
> >             <...>-244     [007] .....     1.959176: asym_cpu_capacity_update_data: -- 160
> >             <...>-244     [007] .....     1.959183: asym_cpu_capacity_update_data: Added new capacity 498. Capacity list order:
> >             <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 1024
> >             <...>-244     [007] .....     1.959184: asym_cpu_capacity_update_data: -- 620
> >             <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 498
> >             <...>-244     [007] .....     1.959185: asym_cpu_capacity_update_data: -- 250
> >             <...>-244     [007] .....     1.959186: asym_cpu_capacity_update_data: -- 160
> >             <...>-244     [007] .....     1.959204: asym_cpu_capacity_scan: Deleted capacity 620
> >             <...>-244     [007] .....     1.959208: asym_cpu_capacity_scan: Deleted capacity 250
> >             <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: Final capacity list order:
> >             <...>-244     [007] .....     1.959209: asym_cpu_capacity_scan: -- 1024
> >             <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 498
> >             <...>-244     [007] .....     1.959210: asym_cpu_capacity_scan: -- 160
> >           rcuop/7-66      [001] b....     1.968114: free_asym_cap_entry: Freeing capacity 620
> >           rcuop/7-66      [001] b....     1.968118: free_asym_cap_entry: Freeing capacity 250
> 
> IMO the trace is not necessary.

Yeah maybe it's a bit too much. I'll drop it.

> 
> > 
> > Suggested-by: Pierre Gondois <pierre.gondois@arm.com>
> > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
> > ---
> >   kernel/sched/topology.c | 16 ++++++++++++++--
> >   1 file changed, 14 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> > index ba4a0b18ae25..1505677e4247 100644
> > --- a/kernel/sched/topology.c
> > +++ b/kernel/sched/topology.c
> > @@ -1384,18 +1384,30 @@ static void free_asym_cap_entry(struct rcu_head *head)
> >   static inline void asym_cpu_capacity_update_data(int cpu)
> >   {
> >   	unsigned long capacity = arch_scale_cpu_capacity(cpu);
> > -	struct asym_cap_data *entry = NULL;
> > +	struct asym_cap_data *insert_entry = NULL;
> > +	struct asym_cap_data *entry;
> > +	/*
> > +	 * Search if capacity already exits. If not, track which the entry
> > +	 * where we should insert to keep the list ordered descendingly.
> > +	 */
> 
> IMO just a small comment like the one suggested below should be enough,
> but this is just a suggestion.

It seems you think it's too verbose but I think your suggestion is too terse
too. Since it is divided into two places and I am combining two operations
I thought it'd be useful to explain what's happening to help read the code at
a glance. I'll keep it as it is for now.


Thanks

--
Qais Yousef
diff mbox series

Patch

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index ba4a0b18ae25..1505677e4247 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1384,18 +1384,30 @@  static void free_asym_cap_entry(struct rcu_head *head)
 static inline void asym_cpu_capacity_update_data(int cpu)
 {
 	unsigned long capacity = arch_scale_cpu_capacity(cpu);
-	struct asym_cap_data *entry = NULL;
+	struct asym_cap_data *insert_entry = NULL;
+	struct asym_cap_data *entry;
 
+	/*
+	 * Search if capacity already exits. If not, track which the entry
+	 * where we should insert to keep the list ordered descendingly.
+	 */
 	list_for_each_entry(entry, &asym_cap_list, link) {
 		if (capacity == entry->capacity)
 			goto done;
+		else if (!insert_entry && capacity > entry->capacity)
+			insert_entry = list_prev_entry(entry, link);
 	}
 
 	entry = kzalloc(sizeof(*entry) + cpumask_size(), GFP_KERNEL);
 	if (WARN_ONCE(!entry, "Failed to allocate memory for asymmetry data\n"))
 		return;
 	entry->capacity = capacity;
-	list_add_rcu(&entry->link, &asym_cap_list);
+
+	/* If NULL then the new capacity is the smallest, add last. */
+	if (!insert_entry)
+		list_add_tail_rcu(&entry->link, &asym_cap_list);
+	else
+		list_add_rcu(&entry->link, &insert_entry->link);
 done:
 	__cpumask_set_cpu(cpu, cpu_capacity_span(entry));
 }