The patch titled
Subject: ksm: add ksm zero pages for each process
has been added to the -mm mm-unstable branch. Its filename is
ksm-add-ksm-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-add-ksm-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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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: xu xin <xu.xin16@xxxxxxxxxx>
Subject: ksm: add ksm zero pages for each process
Date: Tue, 13 Jun 2023 11:09:38 +0800
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. In addition, it help users to know the actual KSM
profit because KSM-placed zero pages are also benefit from KSM.
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
'ksm_zero_pages' in it.
Link: https://lkml.kernel.org/r/20230613030938.185993-1-yang.yang29@xxxxxxxxxx
Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Xiaokai Ran <ran.xiaokai@xxxxxxxxxx>
Reviewed-by: Yang Yang <yang.yang29@xxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: Xuexin Jiang <jiang.xuexin@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 1 +
include/linux/ksm.h | 8 +++++---
include/linux/mm_types.h | 9 +++++++--
mm/khugepaged.c | 2 +-
mm/ksm.c | 1 +
mm/memory.c | 4 ++--
6 files changed, 17 insertions(+), 8 deletions(-)
--- a/fs/proc/base.c~ksm-add-ksm-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, "ksm_zero_pages %lu\n", mm->ksm_zero_pages);
seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
mmput(mm);
--- a/include/linux/ksm.h~ksm-add-ksm-zero-pages-for-each-process
+++ a/include/linux/ksm.h
@@ -35,10 +35,12 @@ void __ksm_exit(struct mm_struct *mm);
extern unsigned long ksm_zero_pages;
-static inline void ksm_might_unmap_zero_page(pte_t pte)
+static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
{
- if (is_ksm_zero_pte(pte))
+ if (is_ksm_zero_pte(pte)) {
ksm_zero_pages--;
+ mm->ksm_zero_pages--;
+ }
}
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
@@ -109,7 +111,7 @@ static inline void ksm_exit(struct mm_st
{
}
-static inline void ksm_might_unmap_zero_page(pte_t pte)
+static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
{
}
--- a/include/linux/mm_types.h~ksm-add-ksm-zero-pages-for-each-process
+++ a/include/linux/mm_types.h
@@ -784,7 +784,7 @@ struct mm_struct {
#ifdef CONFIG_KSM
/*
* Represent how many pages of this process are involved in KSM
- * merging.
+ * merging (not including ksm_zero_pages).
*/
unsigned long ksm_merging_pages;
/*
@@ -792,7 +792,12 @@ struct mm_struct {
* including merged and not merged.
*/
unsigned long ksm_rmap_items;
-#endif
+ /*
+ * Represent how many empty pages are merged with kernel zero
+ * pages when enabling KSM use_zero_pages.
+ */
+ unsigned long ksm_zero_pages;
+#endif /* CONFIG_KSM */
#ifdef CONFIG_LRU_GEN
struct {
/* this mm_struct is on lru_gen_mm_list */
--- a/mm/khugepaged.c~ksm-add-ksm-zero-pages-for-each-process
+++ a/mm/khugepaged.c
@@ -710,7 +710,7 @@ static void __collapse_huge_page_copy_su
spin_lock(ptl);
ptep_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
- ksm_might_unmap_zero_page(pteval);
+ ksm_might_unmap_zero_page(vma->vm_mm, pteval);
}
} else {
src_page = pte_page(pteval);
--- a/mm/ksm.c~ksm-add-ksm-zero-pages-for-each-process
+++ a/mm/ksm.c
@@ -1233,6 +1233,7 @@ static int replace_page(struct vm_area_s
*/
newpte = pte_mkdirty(pte_mkspecial(pfn_pte(page_to_pfn(kpage), vma->vm_page_prot)));
ksm_zero_pages++;
+ mm->ksm_zero_pages++;
/*
* We're replacing an anonymous page with a zero page, which is
* not anonymous. We need to do proper accounting otherwise we
--- a/mm/memory.c~ksm-add-ksm-zero-pages-for-each-process
+++ a/mm/memory.c
@@ -1434,7 +1434,7 @@ static unsigned long zap_pte_range(struc
zap_install_uffd_wp_if_needed(vma, addr, pte, details,
ptent);
if (unlikely(!page)) {
- ksm_might_unmap_zero_page(ptent);
+ ksm_might_unmap_zero_page(mm, ptent);
continue;
}
@@ -3133,7 +3133,7 @@ static vm_fault_t wp_page_copy(struct vm
inc_mm_counter(mm, MM_ANONPAGES);
}
} else {
- ksm_might_unmap_zero_page(vmf->orig_pte);
+ ksm_might_unmap_zero_page(mm, vmf->orig_pte);
inc_mm_counter(mm, MM_ANONPAGES);
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
_
Patches currently in -mm which might be from xu.xin16@xxxxxxxxxx are
ksm-support-unsharing-ksm-placed-zero-pages.patch
ksm-count-all-zero-pages-placed-by-ksm.patch
ksm-add-ksm-zero-pages-for-each-process.patch
ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit.patch
selftest-add-a-testcase-of-ksm-zero-pages.patch
