[PATCH 27/27] drm/amdgpu: Fix GTT size calculation

[Christian König]

Am 28.04.19 um 09:44 schrieb Kuehling, Felix:
> From: Kent Russell <kent.russell at amd.com>
>
> GTT size is currently limited to the minimum of VRAM size or 3/4 of
> system memory. This severely limits the quanitity of system memory
> that can be used by ROCm application.
>
> Increase GTT size to the maximum of VRAM size or system memory size.

Well, NAK.

This limit was done on purpose because we otherwise the max-texture-size 
would be crashing the system because the OOM killer would be causing a 
system panic.

Using more than 75% of system memory by the GPU at the same time makes 
the system unstable and so we can't allow that by default.

What could maybe work is to reduce amount of system memory by a fixed 
factor, but I of hand don't see a way of fixing this in general.

Regards,
Christian.

>
> Signed-off-by: Kent Russell <kent.russell at amd.com>
> Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>
> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index c14198737dcd..e9ecc3953673 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1740,11 +1740,10 @@ 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
> +		gtt_size = max3((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> +				adev->gmc.mc_vram_size,
> +				((uint64_t)si.totalram * si.mem_unit));
> +	} else
>   		gtt_size = (uint64_t)amdgpu_gtt_size << 20;
>   
>   	/* Initialize GTT memory pool */