[PATCH 3/5] drm/amdgpu: fix lru size grouping

[Christian König]

>   	/* custom LRU management */
>   	struct amdgpu_mman_lru			log2_size[AMDGPU_TTM_LRU_SIZE];
> +	struct amdgpu_mman_lru			guard;
> [FK] It would be safer to make the array AMDGPU_TTM_LRU_SIZE+1, instead
> of adding a separate guard afterwards. That way the guard can't get
> accidentally separated by a future change.

Thought about that as well, but decided against it. The crux is just 
that ARRAY_SIZE() won't return the expected value any more.

I'm going to add a comment explaining that this shouldn't be moved apart.

Christian.

Am 17.08.2016 um 23:00 schrieb Felix Kuehling:
> One suggestion inline [FK].
>
> With that fixed, Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>
>
> Regards,
>    Felix
>
>
> On 16-08-17 08:26 AM, Christian König wrote:
>> From: Christian König <christian.koenig at amd.com>
>>
>> Adding a BO can make it the insertion point for larger sizes as well.
>>
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h     | 1 +
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 8 ++++++++
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> index a55eb6f..1f6de92 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> @@ -428,6 +428,7 @@ struct amdgpu_mman {
>>   
>>   	/* custom LRU management */
>>   	struct amdgpu_mman_lru			log2_size[AMDGPU_TTM_LRU_SIZE];
>> +	struct amdgpu_mman_lru			guard;
> [FK] It would be safer to make the array AMDGPU_TTM_LRU_SIZE+1, instead
> of adding a separate guard afterwards. That way the guard can't get
> accidentally separated by a future change.
>
>>   };
>>   
>>   int amdgpu_copy_buffer(struct amdgpu_ring *ring,
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> index f5dc87e..1a12ce0 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> @@ -951,6 +951,8 @@ static struct list_head *amdgpu_ttm_lru_tail(struct ttm_buffer_object *tbo)
>>   	struct list_head *res = lru->lru[tbo->mem.mem_type];
>>   
>>   	lru->lru[tbo->mem.mem_type] = &tbo->lru;
>> +	while ((++lru)->lru[tbo->mem.mem_type] == res)
>> +		lru->lru[tbo->mem.mem_type] = &tbo->lru;
>>   
>>   	return res;
>>   }
>> @@ -961,6 +963,8 @@ static struct list_head *amdgpu_ttm_swap_lru_tail(struct ttm_buffer_object *tbo)
>>   	struct list_head *res = lru->swap_lru;
>>   
>>   	lru->swap_lru = &tbo->swap;
>> +	while ((++lru)->swap_lru == res)
>> +		lru->swap_lru = &tbo->swap;
>>   
>>   	return res;
>>   }
>> @@ -1008,6 +1012,10 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
>>   		lru->swap_lru = &adev->mman.bdev.glob->swap_lru;
>>   	}
>>   
>> +	for (j = 0; j < TTM_NUM_MEM_TYPES; ++j)
>> +		adev->mman.guard.lru[j] = NULL;
>> +	adev->mman.guard.swap_lru = NULL;
>> +
>>   	adev->mman.initialized = true;
>>   	r = ttm_bo_init_mm(&adev->mman.bdev, TTM_PL_VRAM,
>>   				adev->mc.real_vram_size >> PAGE_SHIFT);
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