Re: [PATCH v5 27/40] x86/resctrl: Move thread_throttle_mode_init() to be managed by resctrl

[James Morse]

Hi Reinette,

On 23/10/2024 23:59, Reinette Chatre wrote:
> On 10/4/24 11:03 AM, James Morse wrote:
>> thread_throttle_mode_init() is called from the architecture specific code
>> to make the 'thread_throttle_mode' file visible. The architecture specific
>> code has already set the membw.throttle_mode in the rdt_resource.
>>
>> This doesn't need to be specific to the architecture, the throttle_mode
>> can be used by resctrl to determine if the 'thread_throttle_mode' file
>> should be visible.
>>
>> Call thread_throttle_mode_init() from resctrl_setup(), check the
>> membw.throttle_mode on the MBA resource. This avoids publishing an
>> extra function between the architecture and filesystem code.


>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 3f10e6897daa..596f5f087834 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -2048,10 +2048,15 @@ static struct rftype *rdtgroup_get_rftype_by_name(const char *name)
>>  	return NULL;
>>  }
>>  
>> -void __init thread_throttle_mode_init(void)
>> +static void __init thread_throttle_mode_init(void)
>>  {
>> +	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>>  	struct rftype *rft;
>>  
>> +	if (!r->alloc_capable ||
>> +	    r->membw.throttle_mode == THREAD_THROTTLE_UNDEFINED)
>> +		return;
>> +
> 
> The goal from the changelog is to make "thread_throttle_mode_init()" not be specific
> to an architecture. It does so by checking the value of rdt_resource->resctrl_membw->membw_throttle_mode.
> I thus expect that as part of being non-architectural it should check this for all
> resources that initialize resctrl_membw, this includes RDT_RESOURCE_SMBA.

Sure.

Adding this creates the new corner-case where MBA has a throttle_mode but SMBA does not.
I'll add the corresponding logic to rdt_thread_throttle_mode_show() to print 'undefined'
to user-space if that ever happens.


Thanks,

James