[PATCH 01/10] mm/ksm: reduce the flush action for ksm merging page

alexs
2024-06-04T04:21:35Z

From: "Alex Shi (tencent)" <alexs@kernel.org>

We can put off the flush action util a merging is realy coming. That
could reduce some unmerge page flushing.
BTW, flushing only do at arm, mips and few other archs.

Signed-off-by: Alex Shi (tencent) <alexs@kernel.org>
---
mm/ksm.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index f5138f43f0d2..97e5b41f8c4b 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -783,10 +783,7 @@ static struct page *get_mergeable_page(struct ksm_rmap_item *rmap_item)
goto out;
if (is_zone_device_page(page))
goto out_putpage;
- if (PageAnon(page)) {
- flush_anon_page(vma, page, addr);
- flush_dcache_page(page);
- } else {
+ if (!PageAnon(page)) {
out_putpage:
put_page(page);
out:
@@ -1473,8 +1470,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
*
* This function returns 0 if the pages were merged, -EFAULT otherwise.
*/
-static int try_to_merge_one_page(struct vm_area_struct *vma,
- struct page *page, struct page *kpage)
+static int try_to_merge_one_page(struct vm_area_struct *vma, struct page *page,
+ struct ksm_rmap_item *rmap_item, struct page *kpage)
{
pte_t orig_pte = __pte(0);
int err = -EFAULT;
@@ -1500,6 +1497,9 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
goto out_unlock;
}

+ flush_anon_page(vma, page, rmap_item->address);
+ flush_dcache_page(page);
+
/*
* If this anonymous page is mapped only here, its pte may need
* to be write-protected. If it's mapped elsewhere, all of its
@@ -1550,7 +1550,7 @@ static int try_to_merge_with_ksm_page(struct ksm_rmap_item *rmap_item,
if (!vma)
goto out;

- err = try_to_merge_one_page(vma, page, kpage);
+ err = try_to_merge_one_page(vma, page, rmap_item, kpage);
if (err)
goto out;

@@ -2385,7 +2385,7 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
mmap_read_lock(mm);
vma = find_mergeable_vma(mm, rmap_item->address);
if (vma) {
- err = try_to_merge_one_page(vma, page,
+ err = try_to_merge_one_page(vma, page, rmap_item,
ZERO_PAGE(rmap_item->address));
trace_ksm_merge_one_page(
page_to_pfn(ZERO_PAGE(rmap_item->address)),
@@ -2663,8 +2663,6 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
if (is_zone_device_page(*page))
goto next_page;
if (PageAnon(*page)) {
- flush_anon_page(vma, *page, ksm_scan.address);
- flush_dcache_page(*page);
rmap_item = get_next_rmap_item(mm_slot,
ksm_scan.rmap_list, ksm_scan.address);
if (rmap_item) {
--
2.43.0