Re: [PATCH v7 10/14] arm64/numa: define numa_distance as array to simplify code

[Leizhen (ThunderTown)]

On 2016/8/26 23:29, Will Deacon wrote:
> On Wed, Aug 24, 2016 at 03:44:49PM +0800, Zhen Lei wrote:
>> 1. MAX_NUMNODES is base on CONFIG_NODES_SHIFT, the default value of the
>>latter is very small now.
>> 2. Suppose the default value of MAX_NUMNODES is enlarged to 64, so the
>>size of numa_distance is 4K, it's still acceptable if run the Image
>>on other processors.
>> 3. It will make function __node_distance quicker than before.
>>
>> Signed-off-by: Zhen Lei 
>> ---
>>  arch/arm64/include/asm/numa.h |  1 -
>>  arch/arm64/mm/numa.c  | 74 
>> +++
>>  2 files changed, 5 insertions(+), 70 deletions(-)
> 
> I fail to see the advantages of this patch. Do you have some compelling
> performance figures or something?

We can only put numa_distance_cnt on one node, so for the cpus of other nodes 
to access it should
spend more time. I have not tested how many can be improved yet.

I will try to get some data next week.

> 
> Will
> 
> .
> 

Re: [PATCH v7 10/14] arm64/numa: define numa_distance as array to simplify code

[Leizhen (ThunderTown)]

On 2016/8/26 23:29, Will Deacon wrote:
> On Wed, Aug 24, 2016 at 03:44:49PM +0800, Zhen Lei wrote:
>> 1. MAX_NUMNODES is base on CONFIG_NODES_SHIFT, the default value of the
>>latter is very small now.
>> 2. Suppose the default value of MAX_NUMNODES is enlarged to 64, so the
>>size of numa_distance is 4K, it's still acceptable if run the Image
>>on other processors.
>> 3. It will make function __node_distance quicker than before.
>>
>> Signed-off-by: Zhen Lei 
>> ---
>>  arch/arm64/include/asm/numa.h |  1 -
>>  arch/arm64/mm/numa.c  | 74 
>> +++
>>  2 files changed, 5 insertions(+), 70 deletions(-)
> 
> I fail to see the advantages of this patch. Do you have some compelling
> performance figures or something?

We can only put numa_distance_cnt on one node, so for the cpus of other nodes 
to access it should
spend more time. I have not tested how many can be improved yet.

I will try to get some data next week.

> 
> Will
> 
> .
> 

Re: [PATCH v7 10/14] arm64/numa: define numa_distance as array to simplify code

[Will Deacon]

On Wed, Aug 24, 2016 at 03:44:49PM +0800, Zhen Lei wrote:
> 1. MAX_NUMNODES is base on CONFIG_NODES_SHIFT, the default value of the
>latter is very small now.
> 2. Suppose the default value of MAX_NUMNODES is enlarged to 64, so the
>size of numa_distance is 4K, it's still acceptable if run the Image
>on other processors.
> 3. It will make function __node_distance quicker than before.
> 
> Signed-off-by: Zhen Lei 
> ---
>  arch/arm64/include/asm/numa.h |  1 -
>  arch/arm64/mm/numa.c  | 74 
> +++
>  2 files changed, 5 insertions(+), 70 deletions(-)

I fail to see the advantages of this patch. Do you have some compelling
performance figures or something?

Will

Re: [PATCH v7 10/14] arm64/numa: define numa_distance as array to simplify code

[Will Deacon]

On Wed, Aug 24, 2016 at 03:44:49PM +0800, Zhen Lei wrote:
> 1. MAX_NUMNODES is base on CONFIG_NODES_SHIFT, the default value of the
>latter is very small now.
> 2. Suppose the default value of MAX_NUMNODES is enlarged to 64, so the
>size of numa_distance is 4K, it's still acceptable if run the Image
>on other processors.
> 3. It will make function __node_distance quicker than before.
> 
> Signed-off-by: Zhen Lei 
> ---
>  arch/arm64/include/asm/numa.h |  1 -
>  arch/arm64/mm/numa.c  | 74 
> +++
>  2 files changed, 5 insertions(+), 70 deletions(-)

I fail to see the advantages of this patch. Do you have some compelling
performance figures or something?

Will