Commit 6080d19f authored by xu xin's avatar xu xin Committed by Andrew Morton
Browse files

ksm: add ksm zero pages for each process 

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@zte.com.cn


Signed-off-by: default avatarxu xin <xu.xin16@zte.com.cn>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarXiaokai Ran <ran.xiaokai@zte.com.cn>
Reviewed-by: default avatarYang Yang <yang.yang29@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e2942062

fs/proc/base.c

+1 −0
Original line number Diff line number Diff line
@@ -3207,6 +3207,7 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns, 
	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);

include/linux/ksm.h

+5 −3
Original line number Diff line number Diff line
@@ -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_struct *mm) 
{

}



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)

{

}

include/linux/mm_types.h

+7 −2
Original line number Diff line number Diff line
@@ -812,7 +812,7 @@ 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;

		/*
@@ -820,7 +820,12 @@ 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 */

mm/khugepaged.c

+1 −1
Original line number Diff line number Diff line
@@ -710,7 +710,7 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte, 
				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);

mm/ksm.c

+1 −0
Original line number Diff line number Diff line
@@ -1233,6 +1233,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, 
		 */

		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