linux-kernel - Re: [PATCH v1] x86/sched: Print debug messages on hybrid asym capacity changes

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Message-ID: <20250709114606.GJ1613200@noisy.programming.kicks-ass.net>
Date: Wed, 9 Jul 2025 13:46:06 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: x86 Maintainers <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Linux PM <linux-pm@...r.kernel.org>,
	Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Subject: Re: [PATCH v1] x86/sched: Print debug messages on hybrid asym
 capacity changes

On Wed, Jul 09, 2025 at 12:47:17PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH v1] x86/sched: Print debug messages on hybrid asym capacity changes
> 
> Make arch_set_cpu_capacity() print a debug message including the
> capacity and maximum frequency ratio used in scale-invariant utilization
> computations for a given CPU and in capacity-aware scheduling (CAS) or
> energy-aware scheduling (EAS).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  arch/x86/kernel/cpu/aperfmperf.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> --- a/arch/x86/kernel/cpu/aperfmperf.c
> +++ b/arch/x86/kernel/cpu/aperfmperf.c
> @@ -416,6 +416,10 @@
>  			   div_u64(cap << SCHED_CAPACITY_SHIFT, max_cap));
>  		WRITE_ONCE(per_cpu_ptr(arch_cpu_scale, cpu)->freq_ratio,
>  			   div_u64(cap_freq << SCHED_CAPACITY_SHIFT, base_freq));
> +
> +		pr_debug("CPU%d: capacity = %lu, freq_ratio = %lu\n", cpu,
> +			 per_cpu_ptr(arch_cpu_scale, cpu)->capacity,
> +			 per_cpu_ptr(arch_cpu_scale, cpu)->freq_ratio);
>  	} else {
>  		WARN_ONCE(1, "Hybrid CPU capacity scaling not enabled");
>  	}

There's already a printk in the calling function
hybrid_set_cpu_capacity(), so now we get _2_ prints per CPU. That's a
bit excessive, no?

Also, should this print be conditional on sched_debug_verbose?