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

Yadav, Arvind
2026-03-18T12:16:01Z

On 10-03-2026 15:31, Thomas Hellström wrote:
> 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)
> {
>

Thanks Thomas, that makes sense. I will combine both shrinker helpers
into one and now call it directly from xe_bo_set_purgeable_state(). This
also removes the dual‑call pattern from xe_bo_recompute_purgeable_state()

Thanks,
Arvind

>
>
>
>
>
>