Subject: Re: [PATCH v5 5/6] powerpc/pseries: Add a helper for form1 cpu distance

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Thu, 22 Jul 2021 12:39:27 +0530

David Gibson <[email-masked]> writes:

> On Mon, Jun 28, 2021 at 08:41:16PM +0530, Aneesh Kumar K.V wrote:
>> This helper is only used with the dispatch trace log collection.
>> A later patch will add Form2 affinity support and this change helps
>> in keeping that simpler. Also add a comment explaining we don't expect
>> the code to be called with FORM0
>> 
>> Reviewed-by: David Gibson <[email-masked]>
>> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>
> What makes it a "relative_distance" rather than just a "distance"?

I added that to indicate that the function is not returning the actual
distance but a number indicative of 'near', 'far' etc. (it actually returns
1, 2 etc).

>
>> ---
>>  arch/powerpc/include/asm/topology.h   |  4 ++--
>>  arch/powerpc/mm/numa.c                | 10 +++++++++-
>>  arch/powerpc/platforms/pseries/lpar.c |  4 ++--
>>  3 files changed, 13 insertions(+), 5 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
>> index e4db64c0e184..ac8b5ed79832 100644
>> --- a/arch/powerpc/include/asm/topology.h
>> +++ b/arch/powerpc/include/asm/topology.h
>> @@ -36,7 +36,7 @@ static inline int pcibus_to_node(struct pci_bus *bus)
>>  				 cpu_all_mask :				\
>>  				 cpumask_of_node(pcibus_to_node(bus)))
>>  
>> -extern int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc);
>> +int cpu_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc);
>>  extern int __node_distance(int, int);
>>  #define node_distance(a, b) __node_distance(a, b)
>>  
>> @@ -83,7 +83,7 @@ static inline void sysfs_remove_device_from_node(struct device *dev,
>>  
>>  static inline void update_numa_cpu_lookup_table(unsigned int cpu, int node) {}
>>  
>> -static inline int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>> +static inline int cpu_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>>  {
>>  	return 0;
>>  }
>> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
>> index 7b142f79d600..c6293037a103 100644
>> --- a/arch/powerpc/mm/numa.c
>> +++ b/arch/powerpc/mm/numa.c
>> @@ -166,7 +166,7 @@ static void unmap_cpu_from_node(unsigned long cpu)
>>  }
>>  #endif /* CONFIG_HOTPLUG_CPU || CONFIG_PPC_SPLPAR */
>>  
>> -int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>> +static int __cpu_form1_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>>  {
>>  	int dist = 0;
>>  
>> @@ -182,6 +182,14 @@ int cpu_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>>  	return dist;
>>  }
>>  
>> +int cpu_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
>> +{
>> +	/* We should not get called with FORM0 */
>> +	VM_WARN_ON(affinity_form == FORM0_AFFINITY);
>> +
>> +	return __cpu_form1_relative_distance(cpu1_assoc, cpu2_assoc);
>> +}
>> +
>>  /* must hold reference to node during call */
>>  static const __be32 *of_get_associativity(struct device_node *dev)
>>  {
>> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
>> index dab356e3ff87..afefbdfe768d 100644
>> --- a/arch/powerpc/platforms/pseries/lpar.c
>> +++ b/arch/powerpc/platforms/pseries/lpar.c
>> @@ -261,7 +261,7 @@ static int cpu_relative_dispatch_distance(int last_disp_cpu, int cur_disp_cpu)
>>  	if (!last_disp_cpu_assoc || !cur_disp_cpu_assoc)
>>  		return -EIO;
>>  
>> -	return cpu_distance(last_disp_cpu_assoc, cur_disp_cpu_assoc);
>> +	return cpu_relative_distance(last_disp_cpu_assoc, cur_disp_cpu_assoc);
>>  }
>>  
>>  static int cpu_home_node_dispatch_distance(int disp_cpu)
>> @@ -281,7 +281,7 @@ static int cpu_home_node_dispatch_distance(int disp_cpu)
>>  	if (!disp_cpu_assoc || !vcpu_assoc)
>>  		return -EIO;
>>  
>> -	return cpu_distance(disp_cpu_assoc, vcpu_assoc);
>> +	return cpu_relative_distance(disp_cpu_assoc, vcpu_assoc);
>>  }
>>  
>>  static void update_vcpu_disp_stat(int disp_cpu)
>
> -- 
> David Gibson			| I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
> 				| _way_ _around_!
> http://www.ozlabs.org/~dgibson