+ mm-ksm-add-pages_skipped-metric.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/ksm: add pages_skipped metric
has been added to the -mm mm-unstable branch.  Its filename is
     mm-ksm-add-pages_skipped-metric.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ksm-add-pages_skipped-metric.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Stefan Roesch <shr@devkernel.io>
Subject: mm/ksm: add pages_skipped metric
Date: Mon, 25 Sep 2023 21:09:37 -0700

This change adds the "pages skipped" metric.  To be able to evaluate how
successful smart page scanning is, the pages skipped metric can be
compared to the pages scanned metric.

The pages skipped metric is a cumulative counter.  The counter is stored
under /sys/kernel/mm/ksm/pages_skipped.

Link: https://lkml.kernel.org/r/20230926040939.516161-3-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/mm/ksm.c~mm-ksm-add-pages_skipped-metric
+++ a/mm/ksm.c
@@ -293,6 +293,9 @@ static bool ksm_smart_scan;
 /* The number of zero pages which is placed by KSM */
 unsigned long ksm_zero_pages;
 
+/* The number of pages that have been skipped due to "smart scanning" */
+static unsigned long ksm_pages_skipped;
+
 #ifdef CONFIG_NUMA
 /* Zeroed when merging across nodes is not allowed */
 static unsigned int ksm_merge_across_nodes = 1;
@@ -2376,6 +2379,7 @@ static bool should_skip_rmap_item(struct
 	}
 
 	/* Skip this page */
+	ksm_pages_skipped++;
 	rmap_item->remaining_skips--;
 	remove_rmap_item_from_tree(rmap_item);
 	return true;
@@ -3463,6 +3467,13 @@ static ssize_t pages_volatile_show(struc
 }
 KSM_ATTR_RO(pages_volatile);
 
+static ssize_t pages_skipped_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", ksm_pages_skipped);
+}
+KSM_ATTR_RO(pages_skipped);
+
 static ssize_t ksm_zero_pages_show(struct kobject *kobj,
 				struct kobj_attribute *attr, char *buf)
 {
@@ -3560,6 +3571,7 @@ static struct attribute *ksm_attrs[] = {
 	&pages_sharing_attr.attr,
 	&pages_unshared_attr.attr,
 	&pages_volatile_attr.attr,
+	&pages_skipped_attr.attr,
 	&ksm_zero_pages_attr.attr,
 	&full_scans_attr.attr,
 #ifdef CONFIG_NUMA
_

Patches currently in -mm which might be from shr@devkernel.io are

mm-ksm-support-fork-exec-for-prctl.patch
mm-ksm-test-case-for-prctl-fork-exec-workflow.patch
mm-ksm-add-smart-page-scanning-mode.patch
mm-ksm-add-pages_skipped-metric.patch
mm-ksm-document-smart-scan-mode.patch
mm-ksm-document-pages_skipped-sysfs-knob.patch