Re: [PATCH 17/17] amdgpu: add support for memory cgroups

[David Airlie <airlied@redhat.com>]

On Thu, Jul 3, 2025 at 2:03 AM Shakeel Butt <shakeel.butt@linux.dev> wrote:
>
> On Mon, Jun 30, 2025 at 02:49:36PM +1000, Dave Airlie wrote:
> > From: Dave Airlie <airlied@redhat.com>
> >
> > This adds support for adding a obj cgroup to a buffer object,
> > and passing in the placement flags to make sure it's accounted
> > properly.
> >
> > Signed-off-by: Dave Airlie <airlied@redhat.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c    |  2 ++
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 13 +++++++++----
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_object.h |  1 +
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c    |  2 ++
> >  4 files changed, 14 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > index e5e33a68d935..d250183bab03 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > @@ -198,6 +198,7 @@ static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
> >       struct amdgpu_bo *aobj = gem_to_amdgpu_bo(gobj);
> >
> >       amdgpu_hmm_unregister(aobj);
> > +     obj_cgroup_put(aobj->tbo.objcg);
> >       ttm_bo_put(&aobj->tbo);
> >  }
> >
> > @@ -225,6 +226,7 @@ int amdgpu_gem_object_create(struct amdgpu_device *adev, unsigned long size,
> >       bp.domain = initial_domain;
> >       bp.bo_ptr_size = sizeof(struct amdgpu_bo);
> >       bp.xcp_id_plus1 = xcp_id_plus1;
> > +     bp.objcg = get_obj_cgroup_from_current();
>
> In what context this function is called? Is that the same for
> ttm_pool_alloc_page()? Is remote charging happening in
> ttm_pool_alloc_page()?
>

No, this function is called from userspace ioctl paths that allocate
GPU objects (GEM objects).

The objects are lazily allocated, so this might not trigger any pages
being bound to the object, until it is populated, either via mapping +
page faults or by being used in a GPU command submission, which is
when the ttm_pool_alloc_page happens.

Dave.