[PATCH v3 07/12] drm/xe: Track pagefault worker runtime

[Matthew Brost <matthew.brost@intel.com>]

Add a GT stat measuring total time spent servicing pagefault workqueue
iterations. The counter accumulates the runtime of the pagefault worker
in microseconds, allowing correlation of fault storms and chaining
behavior with CPU time spent in the fault handler.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_gt_stats.c       | 1 +
 drivers/gpu/drm/xe/xe_gt_stats_types.h | 1 +
 drivers/gpu/drm/xe/xe_pagefault.c      | 8 ++++++++
 3 files changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_gt_stats.c b/drivers/gpu/drm/xe/xe_gt_stats.c
index 81cec441b449..c1af3ecb429b 100644
--- a/drivers/gpu/drm/xe/xe_gt_stats.c
+++ b/drivers/gpu/drm/xe/xe_gt_stats.c
@@ -60,6 +60,7 @@ static const char *const stat_description[__XE_GT_STATS_NUM_IDS] = {
 	DEF_STAT_STR(SVM_TLB_INVAL_US, "svm_tlb_inval_us"),
 	DEF_STAT_STR(VMA_PAGEFAULT_COUNT, "vma_pagefault_count"),
 	DEF_STAT_STR(VMA_PAGEFAULT_KB, "vma_pagefault_kb"),
+	DEF_STAT_STR(PAGEFAULT_US, "pagefault_us"),
 	DEF_STAT_STR(INVALID_PREFETCH_PAGEFAULT_COUNT, "invalid_prefetch_pagefault_count"),
 	DEF_STAT_STR(SVM_4K_PAGEFAULT_COUNT, "svm_4K_pagefault_count"),
 	DEF_STAT_STR(SVM_64K_PAGEFAULT_COUNT, "svm_64K_pagefault_count"),
diff --git a/drivers/gpu/drm/xe/xe_gt_stats_types.h b/drivers/gpu/drm/xe/xe_gt_stats_types.h
index b6081c312474..129260bfdfe6 100644
--- a/drivers/gpu/drm/xe/xe_gt_stats_types.h
+++ b/drivers/gpu/drm/xe/xe_gt_stats_types.h
@@ -15,6 +15,7 @@ enum xe_gt_stats_id {
 	XE_GT_STATS_ID_SVM_TLB_INVAL_US,
 	XE_GT_STATS_ID_VMA_PAGEFAULT_COUNT,
 	XE_GT_STATS_ID_VMA_PAGEFAULT_KB,
+	XE_GT_STATS_ID_PAGEFAULT_US,
 	XE_GT_STATS_ID_INVALID_PREFETCH_PAGEFAULT_COUNT,
 	XE_GT_STATS_ID_SVM_4K_PAGEFAULT_COUNT,
 	XE_GT_STATS_ID_SVM_64K_PAGEFAULT_COUNT,
diff --git a/drivers/gpu/drm/xe/xe_pagefault.c b/drivers/gpu/drm/xe/xe_pagefault.c
index a6fa790774c5..030452923ab9 100644
--- a/drivers/gpu/drm/xe/xe_pagefault.c
+++ b/drivers/gpu/drm/xe/xe_pagefault.c
@@ -277,6 +277,8 @@ static void xe_pagefault_queue_work(struct work_struct *w)
 	struct xe_device *xe = pf_work->xe;
 	struct xe_pagefault_queue *pf_queue = &xe->usm.pf_queue;
 	struct xe_pagefault pf;
+	ktime_t start = xe_gt_stats_ktime_get();
+	struct xe_gt *gt = NULL;
 	unsigned long threshold;
 
 #define USM_QUEUE_MAX_RUNTIME_MS      20
@@ -288,6 +290,7 @@ static void xe_pagefault_queue_work(struct work_struct *w)
 		if (!pf.gt)	/* Fault squashed during reset */
 			continue;
 
+		gt = pf.gt;
 		err = xe_pagefault_service(&pf);
 
 		if (err == -EAGAIN) {
@@ -314,6 +317,11 @@ static void xe_pagefault_queue_work(struct work_struct *w)
 		}
 	}
 #undef USM_QUEUE_MAX_RUNTIME_MS
+
+	if (gt)
+		xe_gt_stats_incr(xe_root_mmio_gt(gt_to_xe(gt)),
+				 XE_GT_STATS_ID_PAGEFAULT_US,
+				 xe_gt_stats_ktime_us_delta(start));
 }
 
 static int xe_pagefault_queue_init(struct xe_device *xe,
-- 
2.34.1