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

[Christian König]

Am 19.05.22 um 16:34 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.

It's unfortunately not only the unit tests, but some games as well.

3/4 of total system memory sounds reasonable to be, but I'm 100% sure 
that this will break some tests.

Christian.

>
> 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);