Re: [PATCH v3 5/5] drm/amdgpu: Configure max beneficial TTM pool allocation order

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Thu, 2025-10-09 at 09:58 +0100, Tvrtko Ursulin wrote:
> 
> On 09/10/2025 00:18, Matthew Brost wrote:
> > On Wed, Oct 08, 2025 at 12:53:14PM +0100, Tvrtko Ursulin wrote:
> > > Let the TTM pool allocator know that we can afford for it to
> > > expend less
> > > effort for satisfying contiguous allocations larger than 2MiB.
> > > The latter
> > > is the maximum relevant PTE entry size and the driver and
> > > hardware are
> > > happy to get larger blocks only opportunistically.
> > > 
> > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
> > > Cc: Alex Deucher <alexander.deucher@amd.com>
> > > Cc: Christian König <christian.koenig@amd.com>
> > > Cc: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
> > 
> > +Thomas - Seems like we'd want to do this in Xe too?

Yeah, Indeed.

While IIRC we can actually set up 1GiB PTEs, I'm not aware of any huge
benefits from using that compared to 2MiB ones. We certainly want the
allocator to try pretty hard for 2MiB ones, though.

Thanks,
Thomas


> > 
> > > ---
> > >   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 5 +++--
> > >   1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > > b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > > index 948c6d0a422b..723b885210a7 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > > @@ -1837,7 +1837,7 @@ static int amdgpu_ttm_pools_init(struct
> > > amdgpu_device *adev)
> > >   	for (i = 0; i < adev->gmc.num_mem_partitions; i++) {
> > >   		ttm_pool_init(&adev->mman.ttm_pools[i], adev-
> > > >dev,
> > >   			      adev-
> > > >gmc.mem_partitions[i].numa.node,
> > > -			      0);
> > > +			     
> > > TTM_POOL_BENEFICIAL_ORDER(get_order(2 * SZ_1M)));
> > 
> > SZ_2M btw.
> 
> I thought I grepped exactly to see if that existed but apparently I
> did 
> not, thanks!
> 
> Regards,
> 
> Tvrtko
> 
> > 
> > Matt
> > 
> > >   	}
> > >   	return 0;
> > >   }
> > > @@ -1931,7 +1931,8 @@ int amdgpu_ttm_init(struct amdgpu_device
> > > *adev)
> > >   			       adev_to_drm(adev)->anon_inode-
> > > >i_mapping,
> > >   			       adev_to_drm(adev)-
> > > >vma_offset_manager,
> > >   			       (adev->need_swiotlb ?
> > > TTM_POOL_USE_DMA_ALLOC : 0) |
> > > -			       (dma_addressing_limited(adev-
> > > >dev) ? TTM_POOL_USE_DMA32 : 0));
> > > +			       (dma_addressing_limited(adev-
> > > >dev) ? TTM_POOL_USE_DMA32 : 0) |
> > > +			      
> > > TTM_POOL_BENEFICIAL_ORDER(get_order(2 * SZ_1M)));
> > >   	if (r) {
> > >   		dev_err(adev->dev,
> > >   			"failed initializing buffer object
> > > driver(%d).\n", r);
> > > -- 
> > > 2.48.0
> > > 
>