Re: [PATCH 2/2] drm/amdgpu: add shared fdinfo stats

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

On 09/01/2024 12:54, Daniel Vetter wrote:
> On Tue, Jan 09, 2024 at 09:30:15AM +0000, Tvrtko Ursulin wrote:
>>
>> On 09/01/2024 07:56, Christian König wrote:
>>> Am 07.12.23 um 19:02 schrieb Alex Deucher:
>>>> Add shared stats.  Useful for seeing shared memory.
>>>>
>>>> v2: take dma-buf into account as well
>>>>
>>>> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>>>> Cc: Rob Clark <robdclark@gmail.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c |  4 ++++
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 11 +++++++++++
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_object.h |  6 ++++++
>>>>    3 files changed, 21 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
>>>> index 5706b282a0c7..c7df7fa3459f 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fdinfo.c
>>>> @@ -97,6 +97,10 @@ void amdgpu_show_fdinfo(struct drm_printer *p,
>>>> struct drm_file *file)
>>>>               stats.requested_visible_vram/1024UL);
>>>>        drm_printf(p, "amd-requested-gtt:\t%llu KiB\n",
>>>>               stats.requested_gtt/1024UL);
>>>> +    drm_printf(p, "drm-shared-vram:\t%llu KiB\n",
>>>> stats.vram_shared/1024UL);
>>>> +    drm_printf(p, "drm-shared-gtt:\t%llu KiB\n",
>>>> stats.gtt_shared/1024UL);
>>>> +    drm_printf(p, "drm-shared-cpu:\t%llu KiB\n",
>>>> stats.cpu_shared/1024UL);
>>>> +
>>>>        for (hw_ip = 0; hw_ip < AMDGPU_HW_IP_NUM; ++hw_ip) {
>>>>            if (!usage[hw_ip])
>>>>                continue;
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> index d79b4ca1ecfc..1b37d95475b8 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>>> @@ -1287,25 +1287,36 @@ void amdgpu_bo_get_memory(struct amdgpu_bo *bo,
>>>>                  struct amdgpu_mem_stats *stats)
>>>>    {
>>>>        uint64_t size = amdgpu_bo_size(bo);
>>>> +    struct drm_gem_object *obj;
>>>>        unsigned int domain;
>>>> +    bool shared;
>>>>        /* Abort if the BO doesn't currently have a backing store */
>>>>        if (!bo->tbo.resource)
>>>>            return;
>>>> +    obj = &bo->tbo.base;
>>>> +    shared = (obj->handle_count > 1) || obj->dma_buf;
>>>
>>> I still think that looking at handle_count is the completely wrong
>>> approach, we should really only look at obj->dma_buf.
>>
>> Yeah it is all a bit tricky with the handle table walk. I don't think it is
>> even possible to claim it is shared with obj->dma_buf could be the same
>> process creating say via udmabuf and importing into drm. It is a wild
>> scenario yes, but it could be private memory in that case. Not sure where it
>> would leave us if we said this is just a limitation of a BO based tracking.
>>
>> Would adding a new category "imported" help?
>>
>> Hmm or we simply change drm-usage-stats.rst:
>>
>> """
>> - drm-shared-<region>: <uint> [KiB|MiB]
>>
>> The total size of buffers that are shared with another file (ie. have more
>> than than a single handle).
>> """
>>
>> Changing ie into eg coule be get our of jail free card to allow the
>> "(obj->handle_count > 1) || obj->dma_buf;" condition?
>>
>> Because of the shared with another _file_ wording would cover my wild
>> udmabuf self-import case. Unless there are more such creative private import
>> options.
> 
> Yeah I think clarifying that we can only track sharing with other fd and
> have no idea whether this means sharing with another process or not is
> probably simplest. Maybe not exactly what users want, but still the
> roughly best-case approximation we can deliver somewhat cheaply.
> 
> Also maybe time for a drm_gem_buffer_object_is_shared() helper so we don't
> copypaste this all over and then end up in divergent conditions? I'm
> guessing that there's going to be a bunch of drivers which needs this
> little helper to add drm-shared-* stats to their fdinfo ...

Yeah I agree that works and i915 would need to use the helper too.

I would only suggest to name it so the meaning of shared is obviously 
only about the fdinfo memory stats and no one gets a more meaningful 
idea about its semantics.

We have drm_show_memory_stats and drm_print_memory_stats exported so 
perhaps something like drm_object_is_shared_for_memory_stats, 
drm_object_is_memory_stats_shared, drm_memory_stats_object_is_shared?

And s/ie/eg/ in the above quoted drm-usage-stats.rst.

Regards,

Tvrtko

> 
> Cheers, Sima
>>
>> Regards,
>>
>> Tvrtko
>>
>>>
>>> Regards,
>>> Christian.
>>>
>>>> +
>>>>        domain = amdgpu_mem_type_to_domain(bo->tbo.resource->mem_type);
>>>>        switch (domain) {
>>>>        case AMDGPU_GEM_DOMAIN_VRAM:
>>>>            stats->vram += size;
>>>>            if (amdgpu_bo_in_cpu_visible_vram(bo))
>>>>                stats->visible_vram += size;
>>>> +        if (shared)
>>>> +            stats->vram_shared += size;
>>>>            break;
>>>>        case AMDGPU_GEM_DOMAIN_GTT:
>>>>            stats->gtt += size;
>>>> +        if (shared)
>>>> +            stats->gtt_shared += size;
>>>>            break;
>>>>        case AMDGPU_GEM_DOMAIN_CPU:
>>>>        default:
>>>>            stats->cpu += size;
>>>> +        if (shared)
>>>> +            stats->cpu_shared += size;
>>>>            break;
>>>>        }
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> index d28e21baef16..0503af75dc26 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> @@ -138,12 +138,18 @@ struct amdgpu_bo_vm {
>>>>    struct amdgpu_mem_stats {
>>>>        /* current VRAM usage, includes visible VRAM */
>>>>        uint64_t vram;
>>>> +    /* current shared VRAM usage, includes visible VRAM */
>>>> +    uint64_t vram_shared;
>>>>        /* current visible VRAM usage */
>>>>        uint64_t visible_vram;
>>>>        /* current GTT usage */
>>>>        uint64_t gtt;
>>>> +    /* current shared GTT usage */
>>>> +    uint64_t gtt_shared;
>>>>        /* current system memory usage */
>>>>        uint64_t cpu;
>>>> +    /* current shared system memory usage */
>>>> +    uint64_t cpu_shared;
>>>>        /* sum of evicted buffers, includes visible VRAM */
>>>>        uint64_t evicted_vram;
>>>>        /* sum of evicted buffers due to CPU access */
>>>
>