linux-kernel - Re: [PATCH 03/10] x86/intel_rapl: Modify hot cpu notification handling for RAPL

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Date:	Fri, 5 Jun 2015 17:43:36 -0700 (PDT)
From:	Vikas Shivappa <vikas.shivappa@...el.com>
To:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>
cc:	linux-kernel@...r.kernel.org, vikas.shivappa@...el.com,
	x86@...nel.org, hpa@...or.com, tglx@...utronix.de,
	mingo@...nel.org, tj@...nel.org, peterz@...radead.org,
	Matt Fleming <matt.fleming@...el.com>,
	"Auld, Will" <will.auld@...el.com>,
	"Juvva, Kanaka D" <kanaka.d.juvva@...el.com>, eranian@...gle.com,
	bp@...en8.de, jacob.jun.pan@...ux.intel.com,
	"Kleen, Andi" <andi.kleen@...el.com>
Subject: Re: [PATCH 03/10] x86/intel_rapl: Modify hot cpu notification handling
 for RAPL


+ Andi, Stephan, Boris and Jacob for RAPL patch


On Thu, 4 Jun 2015, Vikas Shivappa wrote:

> This patch modifies the hot cpu notification handling in
> Intel Running Average Power Limit(RAPL) driver.
>
> - to add a cpu reader to the rapl_cpumask(which has one cpu per package
>     set) it uses the existing package<->core map instead of looping
> through all cpus in rapl_cpumask.
> - to search for the next online sibling during hot cpu exit, it uses
> the cpumask_any_online_but instead of looping all online cpus. In
> large systems with large number of cpus the time taken to loop may be
> expensive and also the time increase linearly.
>
> Signed-off-by: Vikas Shivappa <vikas.shivappa@...ux.intel.com>
> ---
> arch/x86/kernel/cpu/perf_event_intel_rapl.c | 27 ++++++++++-----------------
> 1 file changed, 10 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> index 358c54a..987383e 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> @@ -524,18 +524,14 @@ static struct pmu rapl_pmu_class = {
> static void rapl_cpu_exit(int cpu)
> {
> 	struct rapl_pmu *pmu = per_cpu(rapl_pmu, cpu);
> -	int i, phys_id = topology_physical_package_id(cpu);
> 	int target = -1;
> +	int i;
>
> 	/* find a new cpu on same package */
> -	for_each_online_cpu(i) {
> -		if (i == cpu)
> -			continue;
> -		if (phys_id == topology_physical_package_id(i)) {
> -			target = i;
> -			break;
> -		}
> -	}
> +	i = cpumask_any_online_but(topology_core_cpumask(cpu), cpu);
> +	if (i < nr_cpu_ids)
> +		target = i;
> +
> 	/*
> 	 * clear cpu from cpumask
> 	 * if was set in cpumask and still some cpu on package,
> @@ -557,15 +553,12 @@ static void rapl_cpu_exit(int cpu)
>
> static void rapl_cpu_init(int cpu)
> {
> -	int i, phys_id = topology_physical_package_id(cpu);
> +	struct cpumask tmp;
>
> -	/* check if phys_is is already covered */
> -	for_each_cpu(i, &rapl_cpu_mask) {
> -		if (phys_id == topology_physical_package_id(i))
> -			return;
> -	}
> -	/* was not found, so add it */
> -	cpumask_set_cpu(cpu, &rapl_cpu_mask);
> +	/* check if cpu's package is already covered.If not, add it.*/
> +	cpumask_and(&tmp, &rapl_cpu_mask, topology_core_cpumask(cpu));
> +	if (cpumask_empty(&tmp))
> +		cpumask_set_cpu(cpu, &rapl_cpu_mask);
> }
>
> static __init void rapl_hsw_server_quirk(void)
> -- 
> 1.9.1
>
>
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