[PATCH 1/3] drm/amdgpu: Rework KFD memory max limits

[Felix Kuehling]

On 2023-09-29 14:18, Rajneesh Bhardwaj wrote:
> To allow bigger allocations specially on systems such as GFXIP 9.4.3
> that use GTT memory for VRAM allocations, relax the limits to
> maximize ROCm allocations.
>
> Signed-off-by: Rajneesh Bhardwaj <rajneesh.bhardwaj at amd.com>

If the new heuristic in patch 1 causes regressions, we can change 
AMDGPU_RESERVE_MEM_LIMIT to something larger, e.g. 1.5 GB (3UL << 29). 
Maybe we should start with that more conservative value to minimize the 
risk on 16GB system memory systems that have proven problematic in the past.

Other than that, patches 1 and 3 are

Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>


> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index b5b940485059..b1c4e9c0e036 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -42,6 +42,7 @@
>    * changes to accumulate
>    */
>   #define AMDGPU_USERPTR_RESTORE_DELAY_MS 1
> +#define AMDGPU_RESERVE_MEM_LIMIT			(1UL << 30)
>   
>   /*
>    * Align VRAM availability to 2MB to avoid fragmentation caused by 4K allocations in the tail 2MB
> @@ -115,11 +116,16 @@ void amdgpu_amdkfd_gpuvm_init_mem_limits(void)
>   		return;
>   
>   	si_meminfo(&si);
> -	mem = si.freeram - si.freehigh;
> +	mem = si.totalram - si.totalhigh;
>   	mem *= si.mem_unit;
>   
>   	spin_lock_init(&kfd_mem_limit.mem_limit_lock);
> -	kfd_mem_limit.max_system_mem_limit = mem - (mem >> 4);
> +	kfd_mem_limit.max_system_mem_limit = mem - (mem >> 6);
> +	if (kfd_mem_limit.max_system_mem_limit < 2 * AMDGPU_RESERVE_MEM_LIMIT)
> +		kfd_mem_limit.max_system_mem_limit >>= 1;
> +	else
> +		kfd_mem_limit.max_system_mem_limit -= AMDGPU_RESERVE_MEM_LIMIT;
> +
>   	kfd_mem_limit.max_ttm_mem_limit = ttm_tt_pages_limit() << PAGE_SHIFT;
>   	pr_debug("Kernel memory limit %lluM, TTM limit %lluM\n",
>   		(kfd_mem_limit.max_system_mem_limit >> 20),