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

["Iddamsetty, Aravind" <aravind.iddamsetty@intel.com>]

On 26-09-2023 21:12, Tvrtko Ursulin wrote:
> 
> 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.

ya agreed makes no sense.
> 
> 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..

Ok. LGTM

Reviewed-by: Aravind Iddamsetty <aravind.iddamsetty@intel.com>

Thanks,
Aravind.
> 
> Regards,
> 
> Tvrtko