+ ksm-count-zero-pages-for-each-process.patch added to mm-unstable branch

+ ksm-count-zero-pages-for-each-process.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: ksm: count zero pages for each process
has been added to the -mm mm-unstable branch.  Its filename is
     ksm-count-zero-pages-for-each-process.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ksm-count-zero-pages-for-each-process.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: xu xin <xu.xin16@zte.com.cn>
Subject: ksm: count zero pages for each process
Date: Fri, 30 Dec 2022 09:16:29 +0800 (CST)

As the number of ksm zero pages is not included in ksm_merging_pages per
process when enabling use_zero_pages, it's unclear of how many actual
pages are merged by KSM.  To let users accurately estimate their memory
demands when unsharing KSM zero-pages, it's necessary to show KSM zero-
pages per process.

Since unsharing zero pages placed by KSM accurately is achieved, then
tracking empty pages merging and unmerging is not a difficult thing any
longer.

Since we already have /proc/<pid>/ksm_stat, just add the information of
zero_pages_sharing in it.

Link: https://lkml.kernel.org/r/202212300916292181912@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>
Cc: Xiaokai Ran <ran.xiaokai@zte.com.cn>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/fs/proc/base.c~ksm-count-zero-pages-for-each-process
+++ a/fs/proc/base.c
@@ -3207,6 +3207,7 @@ static int proc_pid_ksm_stat(struct seq_
 	mm = get_task_mm(task);
 	if (mm) {
 		seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items);
+		seq_printf(m, "zero_pages_sharing %lu\n", mm->ksm_zero_pages_sharing);
 		mmput(mm);
 	}
 
--- a/include/linux/mm_types.h~ksm-count-zero-pages-for-each-process
+++ a/include/linux/mm_types.h
@@ -776,7 +776,7 @@ struct mm_struct {
 #ifdef CONFIG_KSM
 		/*
 		 * Represent how many pages of this process are involved in KSM
-		 * merging.
+		 * merging (not including ksm_zero_pages_sharing).
 		 */
 		unsigned long ksm_merging_pages;
 		/*
@@ -784,6 +784,11 @@ struct mm_struct {
 		 * including merged and not merged.
 		 */
 		unsigned long ksm_rmap_items;
+		/*
+		 * Represent how many empty pages are merged with kernel zero
+		 * pages when enabling KSM use_zero_pages.
+		 */
+		unsigned long ksm_zero_pages_sharing;
 #endif
 #ifdef CONFIG_LRU_GEN
 		struct {
--- a/mm/ksm.c~ksm-count-zero-pages-for-each-process
+++ a/mm/ksm.c
@@ -794,6 +794,7 @@ static inline void clean_rmap_item_zero_
 {
 	if (rmap_item->address & ZERO_PAGE_FLAG) {
 		ksm_zero_pages_sharing--;
+		rmap_item->mm->ksm_zero_pages_sharing--;
 		rmap_item->address &= PAGE_MASK;
 	}
 }
@@ -2117,6 +2118,7 @@ static int try_to_merge_with_kernel_zero
 			if (!err) {
 				rmap_item->address |= ZERO_PAGE_FLAG;
 				ksm_zero_pages_sharing++;
+				rmap_item->mm->ksm_zero_pages_sharing++;
 			}
 		} else {
 			/* If the vma is out of date, we do not need to continue. */
_

Patches currently in -mm which might be from xu.xin16@zte.com.cn are

ksm-abstract-the-function-try_to_get_old_rmap_item.patch
ksm-support-unsharing-zero-pages-placed-by-ksm.patch
ksm-count-all-zero-pages-placed-by-ksm.patch
ksm-count-zero-pages-for-each-process.patch
ksm-add-zero_pages_sharing-documentation.patch
selftest-add-testing-unsharing-and-counting-ksm-zero-page.patch