Re: [PATCH v3 21/33] drm/xe: Add defrag GT stats

[Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>]

On Fri, Jul 10, 2026 at 07:56:07PM -0700, Matthew Brost wrote:
>Add observability for the page defragmentation worker.
>
>Introduce four primary-GT statistics counters: defrag_added_count
>(BOs queued onto the defrag list after being backed at a sub-optimal
>page order), defrag_success_count (BOs fully re-backed at the beneficial
>order), defrag_partial_success_count (BOs only partially re-backed at the
>beneficial order) defrag_failed_count (attempts that failed and left the
>BO on its original backing) and defrag_mb_moved. The
>ineligible/already-removed fast path is intentionally not counted as
>either success or failure.
>
>Cc: Carlos Santa <carlos.santa@intel.com>
>Cc: Ryan Neph <ryanneph@google.com>
>Cc: Christian Koenig <christian.koenig@amd.com>
>Cc: Huang Rui <ray.huang@amd.com>
>Cc: Matthew Auld <matthew.auld@intel.com>
>Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>Cc: Maxime Ripard <mripard@kernel.org>
>Cc: Thomas Zimmermann <tzimmermann@suse.de>
>Cc: David Airlie <airlied@gmail.com>
>Cc: Simona Vetter <simona@ffwll.ch>
>Cc: dri-devel@lists.freedesktop.org
>Cc: linux-kernel@vger.kernel.org
>Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>Assisted-by: GitHub_Copilot:claude-opus-4.8
>Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>---
> drivers/gpu/drm/xe/xe_bo.c             | 18 +++++++++++++++++-
> drivers/gpu/drm/xe/xe_gt_stats.c       |  5 +++++
> drivers/gpu/drm/xe/xe_gt_stats_types.h | 17 +++++++++++++++++
> 3 files changed, 39 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
>index 907cfa57481f..073d926ef9ac 100644
>--- a/drivers/gpu/drm/xe/xe_bo.c
>+++ b/drivers/gpu/drm/xe/xe_bo.c
>@@ -26,6 +26,7 @@
> #include "xe_dma_buf.h"
> #include "xe_drm_client.h"
> #include "xe_ggtt.h"
>+#include "xe_gt_stats.h"
> #include "xe_map.h"
> #include "xe_migrate.h"
> #include "xe_pat.h"
>@@ -1160,6 +1161,8 @@ static void xe_bo_defrag_add(struct xe_bo *bo)
> 				xe->mem.defrag.interval_ms = XE_BO_DEFRAG_INTERVAL_MS;
> 			list_add_tail(&bo->defrag_link, &xe->mem.defrag.list);
> 			atomic_inc(&xe->mem.defrag.count);
>+			xe_gt_stats_incr(xe_root_mmio_gt(xe),
>+					 XE_GT_STATS_ID_DEFRAG_ADDED_COUNT, 1);

Assisted-by: LLM

I am not sure if ADDED_COUNT is much helpful here. But BOs added here can get silently
dropped. Also, a silently dropped BO can get re-added.

Perhaps a better count would be a 'defrag_pending byte guage'? Also, probably make it
not-resettable so that it gives the current state of fragmentation.

> 		}
> 	}
>
>@@ -1274,8 +1277,21 @@ static int xe_bo_defrag_one(struct xe_device *xe, struct xe_bo *bo,
> 	xe_dbg(xe, "Defrag attempt on BO size=%zu: ret=%pe consumed=%llu\n",
> 	       xe_bo_size(bo), ERR_PTR(ret), *consumed);
>
>-	if (!ret && ttm_tt_is_beneficial_order_failed(bo->ttm.ttm))
>+	if (!ret && ttm_tt_is_beneficial_order_failed(bo->ttm.ttm)) {
> 		*needs_more = true;
>+		xe_gt_stats_incr(xe_root_mmio_gt(xe),
>+				 XE_GT_STATS_ID_DEFRAG_PARTIAL_SUCCESS_COUNT,
>+				 1);
>+	} else {
>+		xe_gt_stats_incr(xe_root_mmio_gt(xe),
>+				 ret ? XE_GT_STATS_ID_DEFRAG_FAILED_COUNT :
>+				       XE_GT_STATS_ID_DEFRAG_SUCCESS_COUNT, 1);
>+	}
>+
>+	if (!ret)
>+		xe_gt_stats_incr(xe_root_mmio_gt(xe),
>+				 XE_GT_STATS_ID_DEFRAG_MB_MOVED,
>+				 *consumed >> 20);

This will truncate the size which can accumulate over multiple BOs and the size
here will be significantly off from real size that is moved.

>
> unlock:
> 	xe_bo_unlock(bo);
>diff --git a/drivers/gpu/drm/xe/xe_gt_stats.c b/drivers/gpu/drm/xe/xe_gt_stats.c
>index 789397514f3e..68e60d9500c8 100644
>--- a/drivers/gpu/drm/xe/xe_gt_stats.c
>+++ b/drivers/gpu/drm/xe/xe_gt_stats.c
>@@ -154,6 +154,11 @@ static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
> 	DEF_STAT_STR(PRL_2M_ENTRY_COUNT, "prl_2m_entry_count"),
> 	DEF_STAT_STR(PRL_ISSUED_COUNT, "prl_issued_count"),
> 	DEF_STAT_STR(PRL_ABORTED_COUNT, "prl_aborted_count"),
>+	DEF_STAT_STR(DEFRAG_ADDED_COUNT, "defrag_added_count"),
>+	DEF_STAT_STR(DEFRAG_SUCCESS_COUNT, "defrag_success_count"),
>+	DEF_STAT_STR(DEFRAG_PARTIAL_SUCCESS_COUNT, "defrag_partial_success_count"),
>+	DEF_STAT_STR(DEFRAG_FAILED_COUNT, "defrag_failed_count"),
>+	DEF_STAT_STR(DEFRAG_MB_MOVED, "defrag_mb_moved"),
> };
>
> /**
>diff --git a/drivers/gpu/drm/xe/xe_gt_stats_types.h b/drivers/gpu/drm/xe/xe_gt_stats_types.h
>index 425491bed6c4..c42b494390f8 100644
>--- a/drivers/gpu/drm/xe/xe_gt_stats_types.h
>+++ b/drivers/gpu/drm/xe/xe_gt_stats_types.h
>@@ -122,6 +122,18 @@
>  * @XE_GT_STATS_ID_PRL_ABORTED_COUNT: Times the page reclaim process was
>  *   aborted.
>  *
>+ * @XE_GT_STATS_ID_DEFRAG_ADDED_COUNT: Times a buffer object was added to the
>+ *   page defragmentation list after being backed at a sub-optimal page order.
>+ * @XE_GT_STATS_ID_DEFRAG_SUCCESS_COUNT: Times the defrag worker successfully
>+ *   re-backed a buffer object at the beneficial page order.
>+ * @XE_GT_STATS_ID_DEFRAG_PARTIAL_SUCCESS_COUNT: Times the defrag worker
>+ *   partially re-backed a buffer object at the beneficial page order.
>+ * @XE_GT_STATS_ID_DEFRAG_FAILED_COUNT: Times the defrag worker failed to
>+ *   re-back a buffer object at the beneficial page order.
>+ * @XE_GT_STATS_ID_DEFRAG_MB_MOVED: Data (MiB) actually (re)allocated while
>+ *   re-backing buffer objects at the beneficial page order. Chunks borrowed
>+ *   from the old backing for free are not counted.
>+ *

NIT...all GTs applied to root GT, which is fine, but probably update stats documentation?

>  * @__XE_GT_STATS_NUM_IDS: Number of valid IDs; not a real counter.
>  *
>  * See Documentation/gpu/xe/xe_gt_stats.rst.
>@@ -181,6 +193,11 @@ enum xe_gt_stats_id {
> 	XE_GT_STATS_ID_PRL_2M_ENTRY_COUNT,
> 	XE_GT_STATS_ID_PRL_ISSUED_COUNT,
> 	XE_GT_STATS_ID_PRL_ABORTED_COUNT,
>+	XE_GT_STATS_ID_DEFRAG_ADDED_COUNT,
>+	XE_GT_STATS_ID_DEFRAG_SUCCESS_COUNT,
>+	XE_GT_STATS_ID_DEFRAG_PARTIAL_SUCCESS_COUNT,
>+	XE_GT_STATS_ID_DEFRAG_FAILED_COUNT,
>+	XE_GT_STATS_ID_DEFRAG_MB_MOVED,

NIT...Few other counts that might be helpful are,
- defrag failure reason (DEFRAG_FAILED_BUSY/ENOMEM)
- time cost of defrag (DEFRAG_US)
- 'removed_without_defrag' so that 'MB_MOVED + removed_without_defrag + defrag_pending'
   is the total suboptimal size added to defrag list.

Niranjana

> 	/* must be the last entry */
> 	__XE_GT_STATS_NUM_IDS,
> };
>-- 
>2.34.1
>