Re: [PATCH v6 10/12] drm/xe/bo: Add purgeable shrinker state helpers

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Tue, 2026-03-03 at 20:50 +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.
> 
> Update purgeable BO state to PURGED after successful shrinker purge
> for DONTNEED BOs.
> 
> 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)
> 
> v6:
>   - Create separate patch for 'Split ghost BO and zero-refcount
>     handling'. (Thomas)
> 
> 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         | 63
> ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_bo.h         |  2 +
>  drivers/gpu/drm/xe/xe_vm_madvise.c |  8 +++-
>  3 files changed, 71 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index 3a4965bdadf2..598d4463baf3 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
> @@ -1243,6 +1303,9 @@ long xe_bo_shrink(struct ttm_operation_ctx
> *ctx, struct ttm_buffer_object *bo,
>  			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 8acc19e25aa5..ab83e94980e4 100644
> --- a/drivers/gpu/drm/xe/xe_vm_madvise.c
> +++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
> @@ -312,12 +312,16 @@ void xe_bo_recompute_purgeable_state(struct
> xe_bo *bo)
>  
>  	if (vma_state == XE_BO_VMAS_STATE_DONTNEED) {
>  		/* 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 if (vma_state == XE_BO_VMAS_STATE_WILLNEED) {
>  		/* 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);
> +		}
>  	}
>  	/* XE_BO_VMAS_STATE_NO_VMAS: Preserve existing BO state */
>  }

I think this can be simplified a bit using something like the below
applied after the above patch: (untested).

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 07acce383cb1..9f0885cd3cfd 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -835,47 +835,14 @@ static int xe_bo_move_notify(struct xe_bo *bo,
 	return 0;
 }
 
-/**
- * xe_bo_set_purgeable_state() - Set BO purgeable state with
validation
- * @bo: Buffer object
- * @new_state: New purgeable state
- *
- * Sets the purgeable state with lockdep assertions and validates
state
- * transitions. Once a BO is PURGED, it cannot transition to any other
state.
- * Invalid transitions are caught with xe_assert().
- */
-void xe_bo_set_purgeable_state(struct xe_bo *bo,
-			       enum xe_madv_purgeable_state new_state)
-{
-	struct xe_device *xe = xe_bo_device(bo);
-
-	xe_bo_assert_held(bo);
-
-	/* Validate state is one of the known values */
-	xe_assert(xe, new_state == XE_MADV_PURGEABLE_WILLNEED ||
-		      new_state == XE_MADV_PURGEABLE_DONTNEED ||
-		      new_state == XE_MADV_PURGEABLE_PURGED);
-
-	/* Once purged, always purged - cannot transition out */
-	xe_assert(xe, !(bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED
&&
-			new_state != XE_MADV_PURGEABLE_PURGED));
-
-	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)
+static void xe_bo_set_purgeable_shrinker(struct xe_bo *bo, enum
xe_madv_purgeable_state new_state)
+					 
 {
 	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;
+	long int tt_pages;
 
 	xe_bo_assert_held(bo);
 
@@ -883,44 +850,44 @@ void xe_bo_set_purgeable_shrinker(struct xe_bo
*bo)
 		return;
 
 	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
-
-	if (!xe_tt->purgeable) {
+	tt_pages = tt->num_pages;
+	
+	if (!xe_tt->purgeable && new_state ==
XE_MADV_PURGEABLE_DONTNEED) {
 		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_shrinker_mod_pages(xe->mem.shrinker, -tt_pages,
tt_pages);
+	} else if (xe_tt->purgeable && new_state ==
XE_MADV_PURGEABLE_WILLNEED) {
+		xe_tt->purgeable = false;
+		xe_shrinker_mod_pages(xe->mem.shrinker, tt_pages, -
tt_pages);
 	}
 }
 
 /**
- * xe_bo_clear_purgeable_shrinker() - Mark BO non-purgeable and update
shrinker
+ * xe_bo_set_purgeable_state() - Set BO purgeable state with
validation
  * @bo: Buffer object
+ * @new_state: New purgeable state
  *
- * Transfers pages from purgeable to shrinkable bucket. Shrinker must
now
- * swap pages instead of discarding. Caller holds BO lock.
+ * Sets the purgeable state with lockdep assertions and validates
state
+ * transitions. Once a BO is PURGED, it cannot transition to any other
state.
+ * Invalid transitions are caught with xe_assert().
  */
-void xe_bo_clear_purgeable_shrinker(struct xe_bo *bo)
+void xe_bo_set_purgeable_state(struct xe_bo *bo
+,			       enum xe_madv_purgeable_state new_state)
 {
-	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;
+	struct xe_device *xe = xe_bo_device(bo);
 
 	xe_bo_assert_held(bo);
 
-	if (!tt || !ttm_tt_is_populated(tt))
-		return;
+	/* Validate state is one of the known values */
+	xe_assert(xe, new_state == XE_MADV_PURGEABLE_WILLNEED ||
+		      new_state == XE_MADV_PURGEABLE_DONTNEED ||
+		      new_state == XE_MADV_PURGEABLE_PURGED);
 
-	xe_tt = container_of(tt, struct xe_ttm_tt, ttm);
+	/* Once purged, always purged - cannot transition out */
+	xe_assert(xe, !(bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED
&&
+			new_state != XE_MADV_PURGEABLE_PURGED));
 
-	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);
-	}
+	bo->madv_purgeable = new_state;
+	xe_bo_set_purgeable_shrinker(bo, new_state);
 }
 
 /**
diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index 46d1fff10e4f..0d9f25b51eb2 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -272,8 +272,6 @@ 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)
 {