[PATCH] drm/amdgpu: simplify vram alloc logic since 2GB limitation removed

[Zhang, Yifan]

[AMD Official Use Only - AMD Internal Distribution Only]

2GB limitation in VRAM allocation is removed in below patch. My patch is a follow up refine for this. The remaing_size calculation was to address the 2GB limitation in contiguous VRAM allocation, and no longer needed after the limitation is removed.

commit b2dba064c9bdd18c7dd39066d25453af28451dbf
Author: Philip Yang <Philip.Yang at amd.com>
Date:   Fri Apr 19 16:27:00 2024 -0400

    drm/amdgpu: Handle sg size limit for contiguous allocation

    Define macro AMDGPU_MAX_SG_SEGMENT_SIZE 2GB, because struct scatterlist
    length is unsigned int, and some users of it cast to a signed int, so
    every segment of sg table is limited to size 2GB maximum.

    For contiguous VRAM allocation, don't limit the max buddy block size in
    order to get contiguous VRAM memory. To workaround the sg table segment
    size limit, allocate multiple segments if contiguous size is bigger than
    AMDGPU_MAX_SG_SEGMENT_SIZE.

    Signed-off-by: Philip Yang <Philip.Yang at amd.com>
    Reviewed-by: Christian König <christian.koenig at amd.com>
    Signed-off-by: Alex Deucher <alexander.deucher at amd.com>



-----Original Message-----
From: Alex Deucher <alexdeucher at gmail.com>
Sent: Tuesday, September 24, 2024 10:07 PM
To: Zhang, Yifan <Yifan1.Zhang at amd.com>
Cc: amd-gfx at lists.freedesktop.org; Yang, Philip <Philip.Yang at amd.com>; Kuehling, Felix <Felix.Kuehling at amd.com>
Subject: Re: [PATCH] drm/amdgpu: simplify vram alloc logic since 2GB limitation removed

On Mon, Sep 23, 2024 at 4:28 AM Yifan Zhang <yifan1.zhang at amd.com> wrote:
>
> Make vram alloc loop simpler after 2GB limitation removed.

Can you provide more context?  What 2GB limitation are you referring to?

Alex

>
> Signed-off-by: Yifan Zhang <yifan1.zhang at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> index 7d26a962f811..3d129fd61fa7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
> @@ -455,7 +455,7 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>         struct amdgpu_bo *bo = ttm_to_amdgpu_bo(tbo);
>         u64 vis_usage = 0, max_bytes, min_block_size;
>         struct amdgpu_vram_mgr_resource *vres;
> -       u64 size, remaining_size, lpfn, fpfn;
> +       u64 size, lpfn, fpfn;
>         unsigned int adjust_dcc_size = 0;
>         struct drm_buddy *mm = &mgr->mm;
>         struct drm_buddy_block *block; @@ -516,25 +516,23 @@ static
> int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>             adev->gmc.gmc_funcs->get_dcc_alignment)
>                 adjust_dcc_size = amdgpu_gmc_get_dcc_alignment(adev);
>
> -       remaining_size = (u64)vres->base.size;
> +       size = (u64)vres->base.size;
>         if (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS && adjust_dcc_size) {
>                 unsigned int dcc_size;
>
>                 dcc_size = roundup_pow_of_two(vres->base.size + adjust_dcc_size);
> -               remaining_size = (u64)dcc_size;
> +               size = (u64)dcc_size;
>
>                 vres->flags |= DRM_BUDDY_TRIM_DISABLE;
>         }
>
>         mutex_lock(&mgr->lock);
> -       while (remaining_size) {
> +       while (true) {
>                 if (tbo->page_alignment)
>                         min_block_size = (u64)tbo->page_alignment << PAGE_SHIFT;
>                 else
>                         min_block_size = mgr->default_page_size;
>
> -               size = remaining_size;
> -
>                 if (bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS && adjust_dcc_size)
>                         min_block_size = size;
>                 else if ((size >= (u64)pages_per_block << PAGE_SHIFT)
> && @@ -562,10 +560,7 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>                 if (unlikely(r))
>                         goto error_free_blocks;
>
> -               if (size > remaining_size)
> -                       remaining_size = 0;
> -               else
> -                       remaining_size -= size;
> +               break;
>         }
>         mutex_unlock(&mgr->lock);
>
> --
> 2.43.0
>