[PATCH v4 8/8] drm/xe/bo: Add purgeable shrinker state helpers

Arvind Yadav
2026-01-20T06:09:31Z

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.

v4:
- @madv_purgeable atomic_t → u32 change across all relevant patches. (Matt)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
drivers/gpu/drm/xe/xe_bo.c | 60 ++++++++++++++++++++++++++++++
drivers/gpu/drm/xe/xe_bo.h | 3 ++
drivers/gpu/drm/xe/xe_vm_madvise.c | 13 +++++--
3 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index cc547915161d..2b1448ea3aed 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -836,6 +836,66 @@ static int xe_bo_move_notify(struct xe_bo *bo,
return 0;
}

+/**
+ * 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
diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
index 00e93b3065c9..681495e905af 100644
--- a/drivers/gpu/drm/xe/xe_bo.h
+++ b/drivers/gpu/drm/xe/xe_bo.h
@@ -270,6 +270,9 @@ static inline bool xe_bo_madv_is_dontneed(struct xe_bo *bo)
return bo->madv_purgeable == XE_MADV_PURGEABLE_DONTNEED;
}

+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)
{
if (likely(bo)) {
diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index 5808fef89777..0fb07a1ed3ae 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -274,12 +274,16 @@ void xe_bo_recheck_purgeable_on_vma_unbind(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) {
bo->madv_purgeable = 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) {
bo->madv_purgeable = XE_MADV_PURGEABLE_WILLNEED;
+ xe_bo_clear_purgeable_shrinker(bo);
+ }
}
}

@@ -325,13 +329,16 @@ static bool xe_vm_madvise_purgeable_bo(struct xe_device *xe, struct xe_vm *vm,

/* Mark VMA WILLNEED - BO becomes non-purgeable immediately */
bo->madv_purgeable = XE_MADV_PURGEABLE_WILLNEED;
+ xe_bo_clear_purgeable_shrinker(bo);
break;
case DRM_XE_VMA_PURGEABLE_STATE_DONTNEED:
vmas[i]->purgeable_state = XE_MADV_PURGEABLE_DONTNEED;

/* Mark BO purgeable only if all VMAs are DONTNEED */
- if (xe_bo_all_vmas_dontneed(bo))
+ if (xe_bo_all_vmas_dontneed(bo)) {
bo->madv_purgeable = XE_MADV_PURGEABLE_DONTNEED;
+ xe_bo_set_purgeable_shrinker(bo);
+ }
break;
default:
drm_warn(&vm->xe->drm, "Invalid madvice value = %d\n",
--
2.43.0