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mm/ksm: add pages scanned metric

PATCH Applied Stefan Roesch 2 participants 2 messages Aug 11, 2023 – Aug 15, 2023

Subsystems (4)
Memory management Documentation MM misc Memory management - KSM (Kernel Samepage Merging)
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Stefan Roesch

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#0 lore raw

PATCH 1/1 mm/ksm: add pages scanned metric

ksm currently maintains several statistics, which let you determine how successful KSM is at sharing pages. However it does not contain a metric to determine how much work it does.

This commit adds the pages scanned metric. This allows the administrator to determine how many pages have been scanned over a period of time.

Signed-off-by Stefan Roesch <[email protected]>
---
 Documentation/admin-guide/mm/ksm.rst |  2 ++
 mm/ksm.c                             | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)
Documentation/admin-guide/mm/ksm.rst +2 -0
index 5c5be7bd84b8..776f244bdae4 100644
@@ -159,6 +159,8 @@ The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
 general_profit
         how effective is KSM. The calculation is explained below.
+pages_scanned
+        how many pages are being scanned for ksm
 pages_shared
         how many shared pages are being used
 pages_sharing
mm/ksm.c +15 -1
index 6b7b8928fb96..8d6aee05421d 100644
@@ -242,6 +242,9 @@ static struct kmem_cache *rmap_item_cache;
 static struct kmem_cache *stable_node_cache;
 static struct kmem_cache *mm_slot_cache;
 
+/* The number of pages scanned */
+static unsigned long ksm_pages_scanned;
+
 /* The number of nodes in the stable tree */
 static unsigned long ksm_pages_shared;
 

@@ -2483,8 +2486,9 @@ static void ksm_do_scan(unsigned int scan_npages)
 {
 	struct ksm_rmap_item *rmap_item;
 	struct page *page;
+	unsigned int npages = scan_npages;
 
-	while (scan_npages-- && likely(!freezing(current))) {
+	while (npages-- && likely(!freezing(current))) {
 		cond_resched();
 		rmap_item = scan_get_next_rmap_item(&page);
 		if (!rmap_item)

@@ -2492,6 +2496,8 @@ static void ksm_do_scan(unsigned int scan_npages)
 		cmp_and_merge_page(page, rmap_item);
 		put_page(page);
 	}
+
+	ksm_pages_scanned += scan_npages - npages;
 }
 
 static int ksmd_should_run(void)

@@ -3332,6 +3338,13 @@ static ssize_t max_page_sharing_store(struct kobject *kobj,
 }
 KSM_ATTR(max_page_sharing);
 
+static ssize_t pages_scanned_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", ksm_pages_scanned);
+}
+KSM_ATTR_RO(pages_scanned);
+
 static ssize_t pages_shared_show(struct kobject *kobj,
 				 struct kobj_attribute *attr, char *buf)
 {

@@ -3440,6 +3453,7 @@ static struct attribute *ksm_attrs[] = {
 	&sleep_millisecs_attr.attr,
 	&pages_to_scan_attr.attr,
 	&run_attr.attr,
+	&pages_scanned_attr.attr,
 	&pages_shared_attr.attr,
 	&pages_sharing_attr.attr,
 	&pages_unshared_attr.attr,

base-commit: f4a280e5bb4a764a75d3215b61bc0f02b4c26417

Signature · 1 line
2.39.3
Acked-by on v1 1/1
#1 lore raw
Quoted 31 lines · Stefan Roesch

ksm currently maintains several statistics, which let you determine how successful KSM is at sharing pages. However it does not contain a metric to determine how much work it does.

This commit adds the pages scanned metric. This allows the administrator to determine how many pages have been scanned over a period of time.

Signed-off-by Stefan Roesch <[email protected]>
---
  Documentation/admin-guide/mm/ksm.rst |  2 ++
  mm/ksm.c                             | 16 +++++++++++++++-
  2 files changed, 17 insertions(+), 1 deletion(-)
Documentation/admin-guide/mm/ksm.rst +2 -0
index 5c5be7bd84b8..776f244bdae4 100644
@@ -159,6 +159,8 @@ The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
  general_profit
          how effective is KSM. The calculation is explained below.
+pages_scanned
+        how many pages are being scanned for ksm
  pages_shared
          how many shared pages are being used
  pages_sharing
mm/ksm.c +0 -0
index 6b7b8928fb96..8d6aee05421d 100644

mm/ksm.c static struct kmem_cache *rmap_item_cache; · line 247

Quoted 6 lines
mm/ksm.c +3 -0
@@ -242,6 +242,9 @@ static struct kmem_cache *rmap_item_cache;
  static struct kmem_cache *stable_node_cache;
  static struct kmem_cache *mm_slot_cache;
 
+/* The number of pages scanned */
+static unsigned long ksm_pages_scanned;
+

LGTM

Acked-by David Hildenbrand <[email protected]>
Signature · 3 lines
Cheers,

David / dhildenb