Re: [PATCH] drm/xe: Use DRM_BUDDY_CONTIGUOUS_ALLOCATION for contiguous allocations

["Yadav, Sanjay Kumar" <sanjay.kumar.yadav@intel.com>]

On 05-12-2025 21:49, Matthew Brost wrote:
> On Fri, Dec 05, 2025 at 08:41:13AM +0530, Sanjay Yadav wrote:
>> The VRAM/stolen memory managers do not currently set
>> DRM_BUDDY_CONTIGUOUS_ALLOCATION for contiguous allocations. Enabling
>> this flag activates the buddy allocator's try_harder path, which helps
>> handle fragmented memory scenarios.
>>
>> This enables the __alloc_contig_try_harder fallback in the buddy
>> allocator, allowing contiguous allocation requests to succeed even when
>> memory is fragmented by combining allocations from both(RHS and LHS)
>> sides of a large free block.
>>
>> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6713
>> Suggested-by: Matthew Auld <matthew.auld@intel.com>
>> Signed-off-by: Sanjay Yadav <sanjay.kumar.yadav@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> index 9f70802fce92..ef6cfb8af0ac 100644
>> --- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> +++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
>> @@ -82,6 +82,9 @@ static int xe_ttm_vram_mgr_new(struct ttm_resource_manager *man,
>>   	if (place->flags & TTM_PL_FLAG_TOPDOWN)
>>   		vres->flags |= DRM_BUDDY_TOPDOWN_ALLOCATION;
>>   
>> +	if (place->flags & TTM_PL_FLAG_CONTIGUOUS)
>> +		vres->flags |= DRM_BUDDY_CONTIGUOUS_ALLOCATION;
> If we set this flag can we remove the logic which rounds the allocation
> size to a pow2 and trims if TTM_PL_FLAG_CONTIGUOUS is set? From a quick
> look it looks we can as drm_buddy has roundup / trim logic if
> DRM_BUDDY_CONTIGUOUS_ALLOCATION is set.
>
> Matt

Thanks for pointing that out! I will incorporate this suggestion in v2 
of the patch.

Sanjay

>
>> +
>>   	if (place->fpfn || lpfn != man->size >> PAGE_SHIFT)
>>   		vres->flags |= DRM_BUDDY_RANGE_ALLOCATION;
>>   
>> -- 
>> 2.52.0
>>