[PATCH] drm/amd/amdgpu: not allow gtt size exceed system memory size

[He, Roger]

-----Original Message-----
From: Christian König [mailto:ckoenig.leichtzumerken at gmail.com] 
Sent: Friday, November 10, 2017 8:02 PM
To: He, Roger <Hongbo.He at amd.com>; amd-gfx at lists.freedesktop.org
Subject: Re: [PATCH] drm/amd/amdgpu: not allow gtt size exceed system memory size

Am 10.11.2017 um 12:33 schrieb Roger He:
> since sometimes VRAM size is bigger than system memory
>
> Change-Id: I5b14d18ed7a9f79810cc50c023ac9e240bddf101
> Signed-off-by: Roger He <Hongbo.He at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index cdbdf67..f103ccc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -1330,9 +1330,14 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>   	DRM_INFO("amdgpu: %uM of VRAM memory ready\n",
>   		 (unsigned) (adev->mc.real_vram_size / (1024 * 1024)));
>   
> -	if (amdgpu_gtt_size == -1)
> -		gtt_size = max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> -			       adev->mc.mc_vram_size);
> +	if (amdgpu_gtt_size == -1) {
> +		struct sysinfo si;
> +
> +		si_meminfo(&si);
> +		gtt_size = min(max((AMDGPU_DEFAULT_GTT_SIZE_MB << 20),
> +			       adev->mc.mc_vram_size),
> +			       ((uint64_t)si.totalram * si.mem_unit));

TTM starts to try to swap things out when more than 50% of system memory are used, 75% is the default hard limit where it starts to block new allocations.

So I would go with 75% here as well and code this as:

gtt_size = AMDGPU_DEFAULT_GTT_SIZE_MB << 20; gtt_size = max(gtt_size, adev->mc.mc_vram_size); gtt_size = min(gtt_size, ((uint64_t)si.totalram * si.mem_unit) * 75 / 100);

[Roger]: but in amdgpu_info_ioctl, for GTT size, reported to UMD already is *3/4
	case AMDGPU_INFO_MEMORY: {
		
		mem.gtt.heap_usage =
			amdgpu_gtt_mgr_usage(&adev->mman.bdev.man[TTM_PL_TT]);
		mem.gtt.max_allocation = mem.gtt.usable_heap_size * 3 / 4;
	
	So is it duplicated  if *75/100 here?


Regards,
Christian.

> +		


> +	}
>   	else
>   		gtt_size = (uint64_t)amdgpu_gtt_size << 20;
>   	r = ttm_bo_init_mm(&adev->mman.bdev, TTM_PL_TT, gtt_size >> 
> PAGE_SHIFT);