Date:   Mon, 27 Feb 2023 09:36:27 -0800
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Subject: [PATCH v4 28/33] mm: introduce per-VMA lock statistics
From:   Suren Baghdasaryan <surenb@google.com>
To:     akpm@linux-foundation.org
Cc:     michel@lespinasse.org, jglisse@google.com, mhocko@suse.com,
        vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net,
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        michalechner92@googlemail.com, linux-mm@kvack.org,
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        linux-kernel@vger.kernel.org, kernel-team@android.com,
        Suren Baghdasaryan <surenb@google.com>
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Precedence: bulk

Add a new CONFIG_PER_VMA_LOCK_STATS config option to dump extra
statistics about handling page fault under VMA lock.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 include/linux/vm_event_item.h | 6 ++++++
 include/linux/vmstat.h        | 6 ++++++
 mm/Kconfig.debug              | 6 ++++++
 mm/memory.c                   | 2 ++
 mm/vmstat.c                   | 6 ++++++
 5 files changed, 26 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 7f5d1caf5890..8abfa1240040 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -149,6 +149,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
 		DIRECT_MAP_LEVEL3_SPLIT,
+#endif
+#ifdef CONFIG_PER_VMA_LOCK_STATS
+		VMA_LOCK_SUCCESS,
+		VMA_LOCK_ABORT,
+		VMA_LOCK_RETRY,
+		VMA_LOCK_MISS,
 #endif
 		NR_VM_EVENT_ITEMS
 };
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 19cf5b6892ce..fed855bae6d8 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -125,6 +125,12 @@ static inline void vm_events_fold_cpu(int cpu)
 #define count_vm_tlb_events(x, y) do { (void)(y); } while (0)
 #endif
 
+#ifdef CONFIG_PER_VMA_LOCK_STATS
+#define count_vm_vma_lock_event(x) count_vm_event(x)
+#else
+#define count_vm_vma_lock_event(x) do {} while (0)
+#endif
+
 #define __count_zid_vm_events(item, zid, delta) \
 	__count_vm_events(item##_NORMAL - ZONE_NORMAL + zid, delta)
 
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index c3547a373c9c..4965a7333a3f 100644
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -279,3 +279,9 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
 
 	  If unsure, say Y.
 
+config PER_VMA_LOCK_STATS
+	bool "Statistics for per-vma locks"
+	depends on PER_VMA_LOCK
+	default y
+	help
+	  Statistics for per-vma locks.
diff --git a/mm/memory.c b/mm/memory.c
index f734f80d28ca..255b2f4fdd4a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5273,6 +5273,7 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
 	/* Check if the VMA got isolated after we found it */
 	if (vma->detached) {
 		vma_end_read(vma);
+		count_vm_vma_lock_event(VMA_LOCK_MISS);
 		/* The area was replaced with another one */
 		goto retry;
 	}
@@ -5281,6 +5282,7 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
 	return vma;
 inval:
 	rcu_read_unlock();
+	count_vm_vma_lock_event(VMA_LOCK_ABORT);
 	return NULL;
 }
 #endif /* CONFIG_PER_VMA_LOCK */
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1ea6a5ce1c41..4f1089a1860e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1399,6 +1399,12 @@ const char * const vmstat_text[] = {
 	"direct_map_level2_splits",
 	"direct_map_level3_splits",
 #endif
+#ifdef CONFIG_PER_VMA_LOCK_STATS
+	"vma_lock_success",
+	"vma_lock_abort",
+	"vma_lock_retry",
+	"vma_lock_miss",
+#endif
 #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
 };
 #endif /* CONFIG_PROC_FS || CONFIG_SYSFS || CONFIG_NUMA || CONFIG_MEMCG */
-- 
2.39.2.722.g9855ee24e9-goog