[PATCH] drm/amdgpu: Adjust logic around GTT size

[Felix Kuehling]

Am 2022-05-19 um 10:34 schrieb Alex Deucher:
> The current somewhat strange logic is in place because certain
> GL unit tests for large textures can cause problems with the
> OOM killer since there is no way to link this memory to a
> process.  The problem is this limit is often too low for many
> modern games on systems with more memory so limit the logic to
> systems with less than 8GB of main memory.  For systems with 8
> or more GB of system memory, set the GTT size to 3/4 of system
> memory.

Well, I've been railing against this limit for years, and was always 
told it's unchangeable for reasons. So we found other ways to use more 
system memory in ROCm. Good to see that I'm no longer the only one who 
thinks this GTT limit is a problem.

Acked-by: Felix Kuehling <Felix.Kuehling at amd.com>


>
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 25 ++++++++++++++++++++-----
>   1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 4b9ee6e27f74..daa0babcf869 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1801,15 +1801,30 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>   	/* Compute GTT size, either bsaed on 3/4th the size of RAM size
>   	 * or whatever the user passed on module init */
>   	if (amdgpu_gtt_size == -1) {
> +		const u64 eight_GB = 8192ULL * 1024 * 1024;
>   		struct sysinfo si;
> +		u64 total_memory, default_gtt_size;
>   
>   		si_meminfo(&si);
> -		gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> -			       adev->gmc.mc_vram_size),
> -			       ((uint64_t)si.totalram * si.mem_unit * 3/4));
> -	}
> -	else
> +		total_memory = (u64)si.totalram * si.mem_unit;
> +		default_gtt_size = total_memory * 3 / 4;
> +		/* This somewhat strange logic is in place because certain GL unit
> +		 * tests for large textures can cause problems with the OOM killer
> +		 * since there is no way to link this memory to a process.
> +		 * The problem is this limit is often too low for many modern games
> +		 * on systems with more memory so limit the logic to systems with
> +		 * less than 8GB of main memory.
> +		 */
> +		if (total_memory < eight_GB) {
> +			gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> +					   adev->gmc.mc_vram_size),
> +				       default_gtt_size);
> +		} else {
> +			gtt_size = default_gtt_size;
> +		}
> +	} else {
>   		gtt_size = (uint64_t)amdgpu_gtt_size << 20;
> +	}
>   
>   	/* Initialize GTT memory pool */
>   	r = amdgpu_gtt_mgr_init(adev, gtt_size);