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

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

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!

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);
> +		}
>  	}
>  }
>