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

[Felix Kuehling]

On 2017-11-10 07:02 AM, Christian König wrote:
> 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:

I believe those limits can be tweaked in
/sys/devices/virtual/drm/ttm/memory_accounting. Therefore I'd be against
hard-coding strict limits in the driver.

Regards,
  Felix

>
> 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);
>
>
> 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);
>
>
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