[RFC PATCH] drm/ttm: Do page counting after populate callback succeed

[Pan, Xinhui]

> 2021年6月15日 20:01，Christian König <ckoenig.leichtzumerken at gmail.com> 写道：
> 
> Am 15.06.21 um 13:57 schrieb xinhui pan:
>> Amdgpu set SG flag in populate callback. So TTM still count pages in SG
>> BO.
> 
> It's probably better to fix this instead. E.g. why does amdgpu modify the SG flag during populate and not during initial creation? That doesn't seem to make sense.

fair enough. Let me have a try.
No idea why we set SG flag in populate years ago.

> 
> Christian.
> 
>> One easy way to fix this is lets count pages after populate callback.
>> 
>> We hit one issue that amdgpu alloc many SG BOs, but TTM try to do swap
>> again and again even if swapout does not swap SG BOs at all.
>> 
>> Signed-off-by: xinhui pan <xinhui.pan at amd.com>
>> ---
>>  drivers/gpu/drm/ttm/ttm_tt.c | 32 +++++++++++++-------------------
>>  1 file changed, 13 insertions(+), 19 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/ttm/ttm_tt.c b/drivers/gpu/drm/ttm/ttm_tt.c
>> index a1a25410ec74..4fa0a8cd71c0 100644
>> --- a/drivers/gpu/drm/ttm/ttm_tt.c
>> +++ b/drivers/gpu/drm/ttm/ttm_tt.c
>> @@ -317,13 +317,6 @@ int ttm_tt_populate(struct ttm_device *bdev,
>>  	if (ttm_tt_is_populated(ttm))
>>  		return 0;
>>  -	if (!(ttm->page_flags & TTM_PAGE_FLAG_SG)) {
>> -		atomic_long_add(ttm->num_pages, &ttm_pages_allocated);
>> -		if (bdev->pool.use_dma32)
>> -			atomic_long_add(ttm->num_pages,
>> -					&ttm_dma32_pages_allocated);
>> -	}
>> -
>>  	while (atomic_long_read(&ttm_pages_allocated) > ttm_pages_limit ||
>>  	       atomic_long_read(&ttm_dma32_pages_allocated) >
>>  	       ttm_dma32_pages_limit) {
>> @@ -342,6 +335,13 @@ int ttm_tt_populate(struct ttm_device *bdev,
>>  	if (ret)
>>  		goto error;
>>  +	if (!(ttm->page_flags & TTM_PAGE_FLAG_SG)) {
>> +		atomic_long_add(ttm->num_pages, &ttm_pages_allocated);
>> +		if (bdev->pool.use_dma32)
>> +			atomic_long_add(ttm->num_pages,
>> +					&ttm_dma32_pages_allocated);
>> +	}
>> +
>>  	ttm_tt_add_mapping(bdev, ttm);
>>  	ttm->page_flags |= TTM_PAGE_FLAG_PRIV_POPULATED;
>>  	if (unlikely(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
>> @@ -355,12 +355,6 @@ int ttm_tt_populate(struct ttm_device *bdev,
>>  	return 0;
>>    error:
>> -	if (!(ttm->page_flags & TTM_PAGE_FLAG_SG)) {
>> -		atomic_long_sub(ttm->num_pages, &ttm_pages_allocated);
>> -		if (bdev->pool.use_dma32)
>> -			atomic_long_sub(ttm->num_pages,
>> -					&ttm_dma32_pages_allocated);
>> -	}
>>  	return ret;
>>  }
>>  EXPORT_SYMBOL(ttm_tt_populate);
>> @@ -384,12 +378,6 @@ void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
>>  	if (!ttm_tt_is_populated(ttm))
>>  		return;
>>  -	ttm_tt_clear_mapping(ttm);
>> -	if (bdev->funcs->ttm_tt_unpopulate)
>> -		bdev->funcs->ttm_tt_unpopulate(bdev, ttm);
>> -	else
>> -		ttm_pool_free(&bdev->pool, ttm);
>> -
>>  	if (!(ttm->page_flags & TTM_PAGE_FLAG_SG)) {
>>  		atomic_long_sub(ttm->num_pages, &ttm_pages_allocated);
>>  		if (bdev->pool.use_dma32)
>> @@ -397,6 +385,12 @@ void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
>>  					&ttm_dma32_pages_allocated);
>>  	}
>>  +	ttm_tt_clear_mapping(ttm);
>> +	if (bdev->funcs->ttm_tt_unpopulate)
>> +		bdev->funcs->ttm_tt_unpopulate(bdev, ttm);
>> +	else
>> +		ttm_pool_free(&bdev->pool, ttm);
>> +
>>  	ttm->page_flags &= ~TTM_PAGE_FLAG_PRIV_POPULATED;
>>  }
>>  
>