Re: [PATCH v4 7/7] selftests/resctrl: Adjust effective L3 cache size when SNC enabled

[Reinette Chatre]

Hi Tony,

On 8/25/2023 10:56 AM, Tony Luck wrote:
> On Fri, Aug 11, 2023 at 10:33:43AM -0700, Reinette Chatre wrote:
>> Hi Tony,
>>
>> On 7/22/2023 12:07 PM, Tony Luck wrote:

...

>>> @@ -190,6 +245,8 @@ int get_cache_size(int cpu_no, char *cache_type, unsigned long *cache_size)
>>>  			break;
>>>  	}
>>>  
>>> +	if (cache_num == 3)
>>> +		*cache_size /= snc_ways();
>>>  	return 0;
>>>  }
>>>  
>>
>> I am surprised that this small change is sufficient. The resctrl
>> selftests are definitely not NUMA aware and the CAT and CMT tests
>> are not taking that into account when picking CPUs to run on. From
>> what I understand LLC occupancy counters need to be added in this
>> scenario but I do not see that done either.
> 
> This is a first step (the tests are definitely going to fail if
> they have incorrect information about the cache size).
> 
> For a fully reliable set of tests some major surgery will be required
> to bind to CPUs and memory to control allocation and access.
> 

What is the plan for making the tests more reliable? What is the
use of this patch if it is just the first step?

Reinette