[PATCH 3/3] drm/amdgpu: add gtt_sys_limit

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On Mon, Jun 26, 2017 at 03:39:57PM +0200, Christian König wrote:
> From: Christian König <christian.koenig at amd.com>
> 
> Limit the size of the GART table for the system domain.
> 
> This saves us a bunch of visible VRAM, but also limitates the maximum BO size we can swap out.
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>

Hmm.

On my system, GTT is 4096MiB (1048576 pages). For this, the table takes up
1048576*8 bytes = 8MiB. Reducing GTT to 256MiB (65536 pages) would reduce the
size of the table to 512 KiB. A relatively large saving, to be sure. But in the
grander scheme of things, is saving 7.5MiB (3% of visible VRAM @ 256M) worth
cutting GTT memory by a factor of 16?

John

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h         | 2 ++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c  | 6 ++++++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c     | 4 ++++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c    | 8 ++++++--
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c     | 2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c | 6 ++++--
>  drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     | 6 +++---
>  7 files changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index ab1dad2..a511029 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -76,6 +76,7 @@
>  extern int amdgpu_modeset;
>  extern int amdgpu_vram_limit;
>  extern int amdgpu_gart_size;
> +extern unsigned amdgpu_gart_sys_limit;
>  extern int amdgpu_moverate;
>  extern int amdgpu_benchmarking;
>  extern int amdgpu_testing;
> @@ -602,6 +603,7 @@ struct amdgpu_mc {
>  	u64			mc_vram_size;
>  	u64			visible_vram_size;
>  	u64			gtt_size;
> +	u64			gtt_sys_limit;
>  	u64			gtt_start;
>  	u64			gtt_end;
>  	u64			vram_start;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 44484bb..b6edb83 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -1122,6 +1122,12 @@ static void amdgpu_check_arguments(struct amdgpu_device *adev)
>  		}
>  	}
>  
> +	if (amdgpu_gart_sys_limit < 32) {
> +		dev_warn(adev->dev, "gart sys limit (%d) too small\n",
> +				 amdgpu_gart_sys_limit);
> +			amdgpu_gart_sys_limit = 32;
> +	}
> +
>  	amdgpu_check_vm_size(adev);
>  
>  	amdgpu_check_block_size(adev);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index 5a1d794..907ae5e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -75,6 +75,7 @@
>  
>  int amdgpu_vram_limit = 0;
>  int amdgpu_gart_size = -1; /* auto */
> +unsigned amdgpu_gart_sys_limit = 256;
>  int amdgpu_moverate = -1; /* auto */
>  int amdgpu_benchmarking = 0;
>  int amdgpu_testing = 0;
> @@ -124,6 +125,9 @@ module_param_named(vramlimit, amdgpu_vram_limit, int, 0600);
>  MODULE_PARM_DESC(gartsize, "Size of PCIE/IGP gart to setup in megabytes (32, 64, etc., -1 = auto)");
>  module_param_named(gartsize, amdgpu_gart_size, int, 0600);
>  
> +MODULE_PARM_DESC(gartlimit, "GART limit for the system domain in megabytes (default 256)");
> +module_param_named(gartlimit, amdgpu_gart_sys_limit, int, 0600);
> +
>  MODULE_PARM_DESC(moverate, "Maximum buffer migration rate in MB/s. (32, 64, etc., -1=auto, 0=1=disabled)");
>  module_param_named(moverate, amdgpu_moverate, int, 0600);
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
> index 8877015..5c6a461 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gart.c
> @@ -70,6 +70,9 @@ void amdgpu_gart_set_defaults(struct amdgpu_device *adev)
>  					adev->mc.mc_vram_size);
>  	else
>  		adev->mc.gtt_size = (uint64_t)amdgpu_gart_size << 20;
> +
> +	adev->mc.gtt_sys_limit = min((uint64_t)amdgpu_gart_sys_limit << 20,
> +				     adev->mc.gtt_size);
>  }
>  
>  /**
> @@ -350,8 +353,9 @@ int amdgpu_gart_init(struct amdgpu_device *adev)
>  	if (r)
>  		return r;
>  	/* Compute table size */
> -	adev->gart.num_cpu_pages = adev->mc.gtt_size / PAGE_SIZE;
> -	adev->gart.num_gpu_pages = adev->mc.gtt_size / AMDGPU_GPU_PAGE_SIZE;
> +	adev->gart.num_cpu_pages = adev->mc.gtt_sys_limit / PAGE_SIZE;
> +	adev->gart.num_gpu_pages = adev->mc.gtt_sys_limit /
> +		AMDGPU_GPU_PAGE_SIZE;
>  	DRM_INFO("GART: num cpu pages %u, num gpu pages %u\n",
>  		 adev->gart.num_cpu_pages, adev->gart.num_gpu_pages);
>  
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 96c4493..6eac481 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -62,7 +62,7 @@ int amdgpu_gem_object_create(struct amdgpu_device *adev, unsigned long size,
>  		/* Maximum bo size is the unpinned gtt size since we use the gtt to
>  		 * handle vram to system pool migrations.
>  		 */
> -		max_size = adev->mc.gtt_size - adev->gart_pin_size;
> +		max_size = adev->mc.gtt_sys_limit - adev->gart_pin_size;
>  		if (size > max_size) {
>  			DRM_DEBUG("Allocation size %ldMb bigger than %ldMb limit\n",
>  				  size >> 20, max_size >> 20);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> index f7d22c4..7609229 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> @@ -42,13 +42,14 @@ struct amdgpu_gtt_mgr {
>  static int amdgpu_gtt_mgr_init(struct ttm_mem_type_manager *man,
>  			       unsigned long p_size)
>  {
> +	struct amdgpu_device *adev = amdgpu_ttm_adev(man->bdev);
>  	struct amdgpu_gtt_mgr *mgr;
>  
>  	mgr = kzalloc(sizeof(*mgr), GFP_KERNEL);
>  	if (!mgr)
>  		return -ENOMEM;
>  
> -	drm_mm_init(&mgr->mm, 0, p_size);
> +	drm_mm_init(&mgr->mm, 0, adev->mc.gtt_sys_limit >> PAGE_SHIFT);
>  	spin_lock_init(&mgr->lock);
>  	mgr->available = p_size;
>  	man->priv = mgr;
> @@ -95,6 +96,7 @@ int amdgpu_gtt_mgr_alloc(struct ttm_mem_type_manager *man,
>  			 const struct ttm_place *place,
>  			 struct ttm_mem_reg *mem)
>  {
> +	struct amdgpu_device *adev = amdgpu_ttm_adev(man->bdev);
>  	struct amdgpu_gtt_mgr *mgr = man->priv;
>  	struct drm_mm_node *node = mem->mm_node;
>  	enum drm_mm_insert_mode mode;
> @@ -112,7 +114,7 @@ int amdgpu_gtt_mgr_alloc(struct ttm_mem_type_manager *man,
>  	if (place && place->lpfn)
>  		lpfn = place->lpfn;
>  	else
> -		lpfn = man->size;
> +		lpfn = adev->gart.num_cpu_pages;
>  
>  	mode = DRM_MM_INSERT_BEST;
>  	if (place && place->flags & TTM_PL_FLAG_TOPDOWN)
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index e4860ac..1e0fcb6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -221,7 +221,7 @@ static void amdgpu_evict_flags(struct ttm_buffer_object *bo,
>  				 * allocating address space for the BO.
>  				 */
>  				abo->placements[i].lpfn =
> -					adev->mc.gtt_size >> PAGE_SHIFT;
> +					adev->gart.num_cpu_pages;
>  			}
>  		}
>  		break;
> @@ -384,7 +384,7 @@ static int amdgpu_move_vram_ram(struct ttm_buffer_object *bo,
>  	placement.num_busy_placement = 1;
>  	placement.busy_placement = &placements;
>  	placements.fpfn = 0;
> -	placements.lpfn = adev->mc.gtt_size >> PAGE_SHIFT;
> +	placements.lpfn = adev->gart.num_cpu_pages;
>  	placements.flags = TTM_PL_MASK_CACHING | TTM_PL_FLAG_TT;
>  	r = ttm_bo_mem_space(bo, &placement, &tmp_mem,
>  			     interruptible, no_wait_gpu);
> @@ -431,7 +431,7 @@ static int amdgpu_move_ram_vram(struct ttm_buffer_object *bo,
>  	placement.num_busy_placement = 1;
>  	placement.busy_placement = &placements;
>  	placements.fpfn = 0;
> -	placements.lpfn = adev->mc.gtt_size >> PAGE_SHIFT;
> +	placements.lpfn = adev->gart.num_cpu_pages;
>  	placements.flags = TTM_PL_MASK_CACHING | TTM_PL_FLAG_TT;
>  	r = ttm_bo_mem_space(bo, &placement, &tmp_mem,
>  			     interruptible, no_wait_gpu);
> -- 
> 2.7.4
> 


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