mm: introduce per-VMA lock statistics

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

Link: https://lkml.kernel.org/r/20230227173632.3292573-29-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 7f5d1ca..8abfa12 100644 (file)
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -150,6 +150,12 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
                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 19cf5b6..fed855b 100644 (file)
--- 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 c3547a3..4965a73 100644 (file)
--- 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 55ac9cd..9999574 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5284,6 +5284,7 @@ retry:
        /* 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;
        }
@@ -5292,6 +5293,7 @@ retry:
        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 b730762..c280463 100644 (file)
--- 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 */