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

Arvind Yadav
2026-03-03T15:21:00Z

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 */
}
--
2.43.0