Re: [PATCH] powercap/rapl: reduce ipi calls

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On Mon, 2015-12-07 at 15:01 -0800, Jacob Pan wrote:
> Reduce remote CPU calls for MSR access by combining read
> modify write into one function.
> 
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
>  drivers/powercap/intel_rapl.c | 91 +++++++++++++++++++++++++++----------------
>  1 file changed, 58 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
> index cc97f08..620c916 100644
> --- a/drivers/powercap/intel_rapl.c
> +++ b/drivers/powercap/intel_rapl.c
> @@ -800,33 +800,43 @@ static int rapl_read_data_raw(struct rapl_domain *rd,
>  	return 0;
>  }
>  
> +struct rapl_msr_action {
> +	u32 msr;
> +	unsigned long long value;
> +	int shift;
> +	u64 mask;
> +};
> +
> +static void rapl_write_data_cpu(void *info)
> +{
> +	u64 msr_val;
> +	struct rapl_msr_action *ra = (struct rapl_msr_action *)info;
> +
> +	rdmsrl_safe(ra->msr, &msr_val);
> +	msr_val &= ~ra->mask;
> +	msr_val |= ra->value << ra->shift;
> +	wrmsrl_safe(ra->msr, msr_val);
What about adding additional common interface
wrmsrl_safe_update(), so that everyone can use this?

> +}
> +
>  /* Similar use of primitive info in the read counterpart */
>  static int rapl_write_data_raw(struct rapl_domain *rd,
>  			enum rapl_primitives prim,
>  			unsigned long long value)
>  {
> -	u64 msr_val;
> -	u32 msr;
> +
> +	struct rapl_msr_action ra;
>  	struct rapl_primitive_info *rp = &rpi[prim];
>  	int cpu;
>  
>  	cpu = find_active_cpu_on_package(rd->package_id);
>  	if (cpu < 0)
>  		return cpu;
> -	msr = rd->msrs[rp->id];
> -	if (rdmsrl_safe_on_cpu(cpu, msr, &msr_val)) {
> -		dev_dbg(&rd->power_zone.dev,
> -			"failed to read msr 0x%x on cpu %d\n", msr, cpu);
> -		return -EIO;
> -	}
> -	value = rapl_unit_xlate(rd, rd->package_id, rp->unit, value, 1);
> -	msr_val &= ~rp->mask;
> -	msr_val |= value << rp->shift;
> -	if (wrmsrl_safe_on_cpu(cpu, msr, msr_val)) {
> -		dev_dbg(&rd->power_zone.dev,
> -			"failed to write msr 0x%x on cpu %d\n", msr, cpu);
> -		return -EIO;
> -	}
> +
> +	ra.msr = rd->msrs[rp->id];
> +	ra.shift = rp->shift;
> +	ra.mask = rp->mask;
> +	ra.value = rapl_unit_xlate(rd, rd->package_id, rp->unit, value, 1);
> +	smp_call_function_single(cpu, rapl_write_data_cpu, &ra, 1);
>  
>  	return 0;
>  }
> @@ -893,6 +903,21 @@ static int rapl_check_unit_atom(struct rapl_package *rp, int cpu)
>  	return 0;
>  }
>  
> +static void power_limit_irq_save_cpu(void *info)
> +{
> +	u32 l, h = 0;
> +	struct rapl_package *rp = (struct rapl_package *)info;
> +
> +	/* save the state of PLN irq mask bit before disabling it */
> +	rdmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
> +	if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED)) {
> +		rp->power_limit_irq = l & PACKAGE_THERM_INT_PLN_ENABLE;
> +		rp->power_limit_irq |= PACKAGE_PLN_INT_SAVED;
> +	}
> +	l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
> +	wrmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
> +}
> +
>  
>  /* REVISIT:
>   * When package power limit is set artificially low by RAPL, LVT
> @@ -906,7 +931,6 @@ static int rapl_check_unit_atom(struct rapl_package *rp, int cpu)
>  
>  static void package_power_limit_irq_save(int package_id)
>  {
> -	u32 l, h = 0;
>  	int cpu;
>  	struct rapl_package *rp;
>  
> @@ -920,20 +944,27 @@ static void package_power_limit_irq_save(int package_id)
>  	cpu = find_active_cpu_on_package(package_id);
>  	if (cpu < 0)
>  		return;
> -	/* save the state of PLN irq mask bit before disabling it */
> -	rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
> -	if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED)) {
> -		rp->power_limit_irq = l & PACKAGE_THERM_INT_PLN_ENABLE;
> -		rp->power_limit_irq |= PACKAGE_PLN_INT_SAVED;
> -	}
> -	l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
> -	wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
> +	smp_call_function_single(cpu, power_limit_irq_save_cpu, rp, 1);
> +}
> +
> +static void power_limit_irq_restore_cpu(void *info)
> +{
> +	u32 l, h = 0;
> +	struct rapl_package *rp = (struct rapl_package *)info;
> +
> +	rdmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
> +
> +	if (rp->power_limit_irq & PACKAGE_THERM_INT_PLN_ENABLE)
> +		l |= PACKAGE_THERM_INT_PLN_ENABLE;
> +	else
> +		l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
> +
> +	wrmsr_safe(MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
>  }
>  
>  /* restore per package power limit interrupt enable state */
>  static void package_power_limit_irq_restore(int package_id)
>  {
> -	u32 l, h;
>  	int cpu;
>  	struct rapl_package *rp;
>  
> @@ -951,14 +982,8 @@ static void package_power_limit_irq_restore(int package_id)
>  	/* irq enable state not saved, nothing to restore */
>  	if (!(rp->power_limit_irq & PACKAGE_PLN_INT_SAVED))
>  		return;
> -	rdmsr_safe_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, &l, &h);
> -
> -	if (rp->power_limit_irq & PACKAGE_THERM_INT_PLN_ENABLE)
> -		l |= PACKAGE_THERM_INT_PLN_ENABLE;
> -	else
> -		l &= ~PACKAGE_THERM_INT_PLN_ENABLE;
>  
> -	wrmsr_on_cpu(cpu, MSR_IA32_PACKAGE_THERM_INTERRUPT, l, h);
> +	smp_call_function_single(cpu, power_limit_irq_restore_cpu, rp, 1);
>  }
>  
>  static void set_floor_freq_default(struct rapl_domain *rd, bool mode)