[PATCH v2 22/33] drm/xe: Add Kconfig.profile options for BO defrag configuration

[Matthew Brost]

Add Kconfig.profile options to make XE_BO_DEFRAG_* defines configurable:
- DRM_XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD: Threshold for TTM reclaim
  backoff
- DRM_XE_BO_DEFRAG_SIZE_LIMIT: Maximum number of bytes to defrag per
  work run
- DRM_XE_BO_DEFRAG_INTERVAL_MS: Default delay before defrag worker runs
- DRM_XE_BO_DEFRAG_INTERVAL_MAX_MS: Upper bound for defrag worker
  interval

Update xe_bo.c to use these Kconfig options as defaults via #ifdef
guards, maintaining backward compatibility with hardcoded values when
not configured.

Additionally, disable defrag completely when XE_BO_DEFRAG_SIZE_LIMIT is
set less than 2M by returning early from xe_bo_defrag_update() (and
xe_bo_defrag_remove()) so BOs are never added to the defrag list or the
worker kicked; xe_bo_defrag_add() and xe_bo_defrag_schedule() assert the
limit is at least 2M.

Cc: Carlos Santa <carlos.santa@xxxxxxxxx>
Cc: Ryan Neph <ryanneph@xxxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Simona Vetter <simona@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Assisted-by: GitHub_Copilot:claude-haiku-4.5
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
---
 drivers/gpu/drm/xe/Kconfig.profile | 40 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_bo.c         | 26 +++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/drivers/gpu/drm/xe/Kconfig.profile b/drivers/gpu/drm/xe/Kconfig.profile
index e07517d120e0..e0aade41f53e 100644
--- a/drivers/gpu/drm/xe/Kconfig.profile
+++ b/drivers/gpu/drm/xe/Kconfig.profile
@@ -74,3 +74,43 @@ config DRM_XE_ENABLE_SCHEDTIMEOUT_LIMIT
 	  to apply to applicable user. For elevated user, all above MIN
 	  and MAX values will apply when this configuration is enable to
 	  apply limitation. By default limitation is applied.
+
+config DRM_XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD
+	int "BO defrag reclaim backoff threshold"
+	default 2
+	range 1 1000
+	help
+	  Once this many BOs are tracked on the device defrag list (i.e. were
+	  backed with a sub-optimal page order), request that the TTM pool backs
+	  off from aggressive reclaim at the beneficial order during populate,
+	  so that allocations make forward progress instead of stalling.
+
+config DRM_XE_BO_DEFRAG_SIZE_LIMIT
+	int "Maximum bytes to defrag per work run"
+	default 33554432
+	range 0 1073741824
+	help
+	  Maximum number of bytes the defrag worker will process in a single run
+	  before yielding and rescheduling itself. Set to less than large page
+	  size (2M) to disable defrag. A defrag move synchronously reallocates
+	  and re-copies a BO's backing store, which is not free. If a large
+	  number of BOs become eligible at once, processing them all in one
+	  worker run would hold things up for a long, unbounded stretch.
+	  Instead, cap the work done per run and requeue, spreading the defrag
+	  effort out over time.
+
+config DRM_XE_BO_DEFRAG_INTERVAL_MS
+	int "Default delay before defrag worker run (ms)"
+	default 25
+	range 1 1000
+	help
+	  Default delay before (re)running the defrag worker, in milliseconds.
+
+config DRM_XE_BO_DEFRAG_INTERVAL_MAX_MS
+	int "Upper bound for defrag worker interval (ms)"
+	default 15000
+	range 100 1000000
+	help
+	  Upper bound for the (exponentially backed off) defrag worker interval,
+	  in milliseconds, so repeated failures don't push the retry arbitrarily
+	  far out. 15000 ms = 15 seconds.
diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index c1bbcf0d21ed..405316d0d116 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -49,7 +49,11 @@
  * aggressive reclaim at the beneficial order during populate, so that
  * allocations make forward progress instead of stalling.
  */
+#ifdef CONFIG_DRM_XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD
+#define XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD	CONFIG_DRM_XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD
+#else
 #define XE_BO_DEFRAG_RECLAIM_BACKOFF_THRESHOLD	2
+#endif
 
 /*
  * Maximum number of bytes of newly (re)allocated backing the defrag worker will
@@ -65,17 +69,31 @@
  * Only pages a move truly reallocates are charged; pages harvested from the old
  * backing are free, so an object larger than the budget is upgraded in
  * budget-sized slices across runs.
+ *
+ * Set to 0 to disable defrag completely.
  */
+#ifdef CONFIG_DRM_XE_BO_DEFRAG_SIZE_LIMIT
+#define XE_BO_DEFRAG_SIZE_LIMIT			CONFIG_DRM_XE_BO_DEFRAG_SIZE_LIMIT
+#else
 #define XE_BO_DEFRAG_SIZE_LIMIT			SZ_32M
+#endif
 
 /* Default delay before (re)running the defrag worker, in milliseconds. */
+#ifdef CONFIG_DRM_XE_BO_DEFRAG_INTERVAL_MS
+#define XE_BO_DEFRAG_INTERVAL_MS		CONFIG_DRM_XE_BO_DEFRAG_INTERVAL_MS
+#else
 #define XE_BO_DEFRAG_INTERVAL_MS		25
+#endif
 
 /*
  * Upper bound for the (exponentially backed off) defrag worker interval, in
  * milliseconds, so repeated failures don't push the retry arbitrarily far out.
  */
+#ifdef CONFIG_DRM_XE_BO_DEFRAG_INTERVAL_MAX_MS
+#define XE_BO_DEFRAG_INTERVAL_MAX_MS		CONFIG_DRM_XE_BO_DEFRAG_INTERVAL_MAX_MS
+#else
 #define XE_BO_DEFRAG_INTERVAL_MAX_MS		15000	/* 15 seconds */
+#endif
 
 static void xe_bo_defrag_worker(struct work_struct *w);
 static void xe_place_from_ttm_type(u32 mem_type, struct ttm_place *place);
@@ -1120,6 +1138,7 @@ int xe_bo_defrag_init(struct xe_device *xe)
 
 static void xe_bo_defrag_schedule(struct xe_device *xe)
 {
+	xe_assert(xe, XE_BO_DEFRAG_SIZE_LIMIT >= SZ_2M);
 	schedule_delayed_work(&xe->mem.defrag.worker,
 			      msecs_to_jiffies(xe->mem.defrag.interval_ms));
 }
@@ -1146,6 +1165,7 @@ static void xe_bo_defrag_add(struct xe_bo *bo)
 
 	xe_bo_assert_held(bo);
 	xe_assert(xe, xe_bo_needs_defrag(bo));
+	xe_assert(xe, XE_BO_DEFRAG_SIZE_LIMIT >= SZ_2M);
 
 	scoped_guard(spinlock, &xe->mem.defrag.lock) {
 		if (list_empty(&bo->defrag_link)) {
@@ -1179,6 +1199,9 @@ static void xe_bo_defrag_remove(struct xe_bo *bo)
 {
 	xe_bo_assert_held(bo);
 
+	if (XE_BO_DEFRAG_SIZE_LIMIT < SZ_2M)
+		return;
+
 	if (list_empty(&bo->defrag_link))
 		return;
 
@@ -1198,6 +1221,9 @@ static void xe_bo_defrag_update(struct xe_bo *bo)
 {
 	xe_bo_assert_held(bo);
 
+	if (XE_BO_DEFRAG_SIZE_LIMIT < SZ_2M)
+		return;
+
 	if (xe_bo_needs_defrag(bo))
 		xe_bo_defrag_add(bo);
 	else
-- 
2.34.1