Re: [PATCH v5 8/9] drm/xe/bo: Add purgeable shrinker state helpers

["Yadav, Arvind" <arvind.yadav@intel.com>]

On 24-02-2026 19:51, Thomas Hellström wrote:
> On Wed, 2026-02-11 at 20:56 +0530, Arvind Yadav wrote:
>> Encapsulate TTM purgeable flag updates and shrinker page accounting
>> into helper functions. This prevents desynchronization between the
>> TTM tt->purgeable flag and the shrinker's page bucket counters.
>>
>> Without these helpers, direct manipulation of xe_ttm_tt->purgeable
>> risks forgetting to update the corresponding shrinker counters,
>> leading to incorrect memory pressure calculations.
>>
>> Add xe_bo_set_purgeable_shrinker() and
>> xe_bo_clear_purgeable_shrinker()
>> which atomically update both the TTM flag and transfer pages between
>> the shrinkable and purgeable buckets.
>>
>> Handle ghost BOs and zero-refcount xe BOs separately in
>> xe_bo_shrink().
>> Ghost BOs from ttm_bo_pipeline_gutting() still hold reclaimable
>> pages,
>> so attempt the shrink to let the shrinker block until the fence
>> signals.
>> For xe BOs whose refcount has dropped to zero, return -EBUSY since
>> the
>> destroy path will handle cleanup.
>>
>> v4:
>>    - @madv_purgeable atomic_t → u32 change across all relevant
>>      patches (Matt)
>>
>> v5:
>>    - Update purgeable BO state to PURGED after a successful shrinker
>>      purge for DONTNEED BOs.
>>    - Split ghost BO and zero-refcount handling in xe_bo_shrink()
>> (Thomas)
> You'd need to split this patch so that the zero-refcount fix gets into
> a separate patch with a Fixes: tag!


Noted, I will create separate patch .

Thanks,
Arvind

>
> Otherwise LGTM.
>
>
>> Cc: Matthew Brost <matthew.brost@intel.com>
>> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_bo.c         | 69
>> +++++++++++++++++++++++++++++-
>>   drivers/gpu/drm/xe/xe_bo.h         |  2 +
>>   drivers/gpu/drm/xe/xe_vm_madvise.c |  8 +++-
>>   3 files changed, 76 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
>> index 7ee85c8eadde..9484105708f7 100644
>> --- a/drivers/gpu/drm/xe/xe_bo.c
>> +++ b/drivers/gpu/drm/xe/xe_bo.c
>> @@ -863,6 +863,66 @@ void xe_bo_set_purgeable_state(struct xe_bo *bo,
>>   	bo->madv_purgeable = new_state;
>>   }
>>   
>> +/**
>> + * xe_bo_set_purgeable_shrinker() - Mark BO purgeable and update
>> shrinker
>> + * @bo: Buffer object
>> + *
>> + * Transfers pages from shrinkable to purgeable bucket. Shrinker can
>> now
>> + * discard pages immediately without swapping. Caller holds BO lock.
>> + */
>> +void xe_bo_set_purgeable_shrinker(struct xe_bo *bo)
>> +{
>> +	struct ttm_buffer_object *ttm_bo = &bo->ttm;
>> +	struct ttm_tt *tt = ttm_bo->ttm;
>> +	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
>> +	struct xe_ttm_tt *xe_tt;
>> +
>> +	xe_bo_assert_held(bo);
>> +
>> +	if (!tt || !ttm_tt_is_populated(tt))
>> +		return;
>> +
>> +	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
>> +
>> +	if (!xe_tt->purgeable) {
>> +		xe_tt->purgeable = true;
>> +		/* Transfer pages from shrinkable to purgeable count
>> */
>> +		xe_shrinker_mod_pages(xe->mem.shrinker,
>> +				      -(long)tt->num_pages,
>> +				      tt->num_pages);
>> +	}
>> +}
>> +
>> +/**
>> + * xe_bo_clear_purgeable_shrinker() - Mark BO non-purgeable and
>> update shrinker
>> + * @bo: Buffer object
>> + *
>> + * Transfers pages from purgeable to shrinkable bucket. Shrinker
>> must now
>> + * swap pages instead of discarding. Caller holds BO lock.
>> + */
>> +void xe_bo_clear_purgeable_shrinker(struct xe_bo *bo)
>> +{
>> +	struct ttm_buffer_object *ttm_bo = &bo->ttm;
>> +	struct ttm_tt *tt = ttm_bo->ttm;
>> +	struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
>> +	struct xe_ttm_tt *xe_tt;
>> +
>> +	xe_bo_assert_held(bo);
>> +
>> +	if (!tt || !ttm_tt_is_populated(tt))
>> +		return;
>> +
>> +	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
>> +
>> +	if (xe_tt->purgeable) {
>> +		xe_tt->purgeable = false;
>> +		/* Transfer pages from purgeable to shrinkable count
>> */
>> +		xe_shrinker_mod_pages(xe->mem.shrinker,
>> +				      tt->num_pages,
>> +				      -(long)tt->num_pages);
>> +	}
>> +}
>> +
>>   /**
>>    * xe_ttm_bo_purge() - Purge buffer object backing store
>>    * @ttm_bo: The TTM buffer object to purge
>> @@ -1234,14 +1294,21 @@ long xe_bo_shrink(struct ttm_operation_ctx
>> *ctx, struct ttm_buffer_object *bo,
>>   	if (!xe_bo_eviction_valuable(bo, &place))
>>   		return -EBUSY;
>>   
>> -	if (!xe_bo_is_xe_bo(bo) || !xe_bo_get_unless_zero(xe_bo))
>> +	/* Ghost BOs still hold reclaimable pages, try to shrink
>> them. */
>> +	if (!xe_bo_is_xe_bo(bo))
>>   		return xe_bo_shrink_purge(ctx, bo, scanned);
>>   
>> +	if (!xe_bo_get_unless_zero(xe_bo))
>> +		return -EBUSY;
>> +
>>   	if (xe_tt->purgeable) {
>>   		if (bo->resource->mem_type != XE_PL_SYSTEM)
>>   			lret = xe_bo_move_notify(xe_bo, ctx);
>>   		if (!lret)
>>   			lret = xe_bo_shrink_purge(ctx, bo, scanned);
>> +		if (lret > 0 && xe_bo_madv_is_dontneed(xe_bo))
>> +			xe_bo_set_purgeable_state(xe_bo,
>> +						
>> XE_MADV_PURGEABLE_PURGED);
>>   		goto out_unref;
>>   	}
>>   
>> diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
>> index 0d9f25b51eb2..46d1fff10e4f 100644
>> --- a/drivers/gpu/drm/xe/xe_bo.h
>> +++ b/drivers/gpu/drm/xe/xe_bo.h
>> @@ -272,6 +272,8 @@ static inline bool xe_bo_madv_is_dontneed(struct
>> xe_bo *bo)
>>   }
>>   
>>   void xe_bo_set_purgeable_state(struct xe_bo *bo, enum
>> xe_madv_purgeable_state new_state);
>> +void xe_bo_set_purgeable_shrinker(struct xe_bo *bo);
>> +void xe_bo_clear_purgeable_shrinker(struct xe_bo *bo);
>>   
>>   static inline void xe_bo_unpin_map_no_vm(struct xe_bo *bo)
>>   {
>> diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c
>> b/drivers/gpu/drm/xe/xe_vm_madvise.c
>> index 8d55ea78b6d1..235fff2b654e 100644
>> --- a/drivers/gpu/drm/xe/xe_vm_madvise.c
>> +++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
>> @@ -289,12 +289,16 @@ void xe_bo_recompute_purgeable_state(struct
>> xe_bo *bo)
>>   
>>   	if (xe_bo_all_vmas_dontneed(bo)) {
>>   		/* All VMAs are DONTNEED - mark BO purgeable */
>> -		if (bo->madv_purgeable !=
>> XE_MADV_PURGEABLE_DONTNEED)
>> +		if (bo->madv_purgeable !=
>> XE_MADV_PURGEABLE_DONTNEED) {
>>   			xe_bo_set_purgeable_state(bo,
>> XE_MADV_PURGEABLE_DONTNEED);
>> +			xe_bo_set_purgeable_shrinker(bo);
>> +		}
>>   	} else {
>>   		/* At least one VMA is WILLNEED - BO must not be
>> purgeable */
>> -		if (bo->madv_purgeable !=
>> XE_MADV_PURGEABLE_WILLNEED)
>> +		if (bo->madv_purgeable !=
>> XE_MADV_PURGEABLE_WILLNEED) {
>>   			xe_bo_set_purgeable_state(bo,
>> XE_MADV_PURGEABLE_WILLNEED);
>> +			xe_bo_clear_purgeable_shrinker(bo);
>> +		}
>>   	}
>>   }
>>