[PATCH] drm/amdgpu: Adjust logic around GTT size (v3)

[Marek Olšák]

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Fri, May 20, 2022 at 11:09 AM Alex Deucher <alexander.deucher at amd.com>
wrote:

> 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 1/2
> 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 max(3G, 1/2 of system ram) by default.
>
> v2: drop previous logic and default to 3/4 of ram
> v3: default to half of ram to align with ttm
>
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index d2b5cccb45c3..7195ed77c85a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1798,18 +1798,26 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>         DRM_INFO("amdgpu: %uM of VRAM memory ready\n",
>                  (unsigned) (adev->gmc.real_vram_size / (1024 * 1024)));
>
> -       /* Compute GTT size, either bsaed on 3/4th the size of RAM size
> +       /* Compute GTT size, either bsaed on 1/2 the size of RAM size
>          * or whatever the user passed on module init */
>         if (amdgpu_gtt_size == -1) {
>                 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 1/2
> +                * of system memory which aligns with TTM. 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 = max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> +                              (u64)si.totalram * si.mem_unit / 2);
> +       } else {
>                 gtt_size = (uint64_t)amdgpu_gtt_size << 20;
> +       }
>
>         /* Initialize GTT memory pool */
>         r = amdgpu_gtt_mgr_init(adev, gtt_size);
> --
> 2.35.3
>
>
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