Re: [PATCH] drm/amdgpu: Adjust logic around GTT size (v2)

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 19.05.22 um 17:57 schrieb Alex Deucher:
> 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.  This was originally mitigated (but not necessarily
> eliminated) by limiting the GTT size.  The problem is this limit
> is often too low for many modern games so just make the limit 3/4
> of system memory. The OOM accounting needs to be addressed, but
> we shouldn't prevent common 3D applications from being usable
> just to potentially mitigate that corner case.
>
> Set default GTT size to 3/4 of system ram by default.
>
> v2: drop previous logic and default to 3/4 of ram

Well that is a pretty clear NAK.

This will cause massive problems for some test cases.

Christian.

>
> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 17 ++++++++++++-----
>   1 file changed, 12 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..4966412024a3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1804,12 +1804,19 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>   		struct sysinfo si;
>   
>   		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
> +		/* 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.  This was originally mitigated (but not necessarily
> +		 * eliminated) by limiting the GTT size.  The problem is this limit
> +		 * is often too low for many modern games so just make the limit 3/4
> +		 * of system memory. The OOM accounting needs to be addressed, but
> +		 * we shouldn't prevent common 3D applications from being usable
> +		 * just to potentially mitigate that corner case.
> +		 */
> +		gtt_size = (u64)si.totalram * si.mem_unit * 3 / 4;
> +	} else {
>   		gtt_size = (uint64_t)amdgpu_gtt_size << 20;
> +	}
>   
>   	/* Initialize GTT memory pool */
>   	r = amdgpu_gtt_mgr_init(adev, gtt_size);