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

[Tvrtko Ursulin]

On 26/09/2023 16:29, Iddamsetty, Aravind wrote:
On 22-09-2023 19:16, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursu...@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.ursu...@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