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Date: Tue, 2 Jan 2024 18:09:54 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: Qais Yousef <qyousef@...alina.io>, Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] sched/topology: Sort asym_cap_list in descending
order
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@....com>
> Signed-off-by: Qais Yousef (Google) <qyousef@...alina.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));
> }
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