Re: [PATCH 5/6] drm/i915: Add stable memory region names

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/09/2023 16:29, Iddamsetty, Aravind wrote:
> On 22-09-2023 19:16, Tvrtko Ursulin wrote:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> At the moment memory region names are a bit too varied and too
>> inconsistent to be used for ABI purposes, like for upcoming fdinfo
>> memory stats.
>>
>> System memory can be either system or system-ttm. Local memory has the
>> instance number appended, others do not. Not only incosistent but thi
>> kind of implementation detail is uninteresting for intended users of
>> fdinfo memory stats.
>>
>> Add a stable name always formed as $type$instance. Could have chosen a
>> different stable scheme, but I think any consistent and stable scheme
>> should do just fine.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_memory_region.c | 19 +++++++++++++++++++
>>   drivers/gpu/drm/i915/intel_memory_region.h |  1 +
>>   2 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
>> index 3d1fdea9811d..60a03340bbd4 100644
>> --- a/drivers/gpu/drm/i915/intel_memory_region.c
>> +++ b/drivers/gpu/drm/i915/intel_memory_region.c
>> @@ -216,6 +216,22 @@ static int intel_memory_region_memtest(struct intel_memory_region *mem,
>>   	return err;
>>   }
>>   
>> +static const char *region_type_str(u16 type)
>> +{
>> +	switch (type) {
>> +	case INTEL_MEMORY_SYSTEM:
>> +		return "system";
>> +	case INTEL_MEMORY_LOCAL:
>> +		return "local";
>> +	case INTEL_MEMORY_STOLEN_LOCAL:
>> +		return "stolen-local";
>> +	case INTEL_MEMORY_STOLEN_SYSTEM:
>> +		return "stolen-system";
>> +	default:
>> +		return "unknown";
>> +	}
>> +}
>> +
>>   struct intel_memory_region *
>>   intel_memory_region_create(struct drm_i915_private *i915,
>>   			   resource_size_t start,
>> @@ -244,6 +260,9 @@ intel_memory_region_create(struct drm_i915_private *i915,
>>   	mem->type = type;
>>   	mem->instance = instance;
>>   
>> +	snprintf(mem->uabi_name, sizeof(mem->uabi_name), "%s%u",
>> +		 region_type_str(type), instance);
>> +
>>   	mutex_init(&mem->objects.lock);
>>   	INIT_LIST_HEAD(&mem->objects.list);
>>   
>> diff --git a/drivers/gpu/drm/i915/intel_memory_region.h b/drivers/gpu/drm/i915/intel_memory_region.h
>> index 2953ed5c3248..9ba36454e51b 100644
>> --- a/drivers/gpu/drm/i915/intel_memory_region.h
>> +++ b/drivers/gpu/drm/i915/intel_memory_region.h
>> @@ -80,6 +80,7 @@ struct intel_memory_region {
>>   	u16 instance;
>>   	enum intel_region_id id;
>>   	char name[16];
>> +	char uabi_name[16];
> 
> Just a thought instead of creating a new field, can't we derive this
> with name and instance?

I'd rather not snprintf on every fdinfo read - for every pid and every 
drm fd versus 2-3 strings kept around.

I did briefly wonder if mr->name could be dropped, that is renamed to 
mr->uabi_name, but I guess there is some value to print the internal 
name in some log messages, to leave a trace of what underlying 
implementation is used. Although I am not too sure about the value of 
that either since it is implied from the kernel version.

Then on top the usage in i915_gem_create/repr_name I could replace with 
mr->uabi_name and simplify. If there is any value in printing the name 
there, versus just uabi type:instance integers. Dunno. All I know is 
fdinfo should have stable names and not confuse with implementation 
details so I need something..

Regards,

Tvrtko