[PATCH 10/10] m/ksm: use folio in ksm scan path

alexs
2024-06-04T04:22:01Z

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

Now we could safely use folio in ksm_do_scan path to save a few compound
checks. The 'page' still used since follow_page function still no folio
version.

Signed-off-by: Alex Shi (tencent) <alexs@kernel.org>
---
mm/ksm.c | 47 +++++++++++++++++++++++++----------------------
1 file changed, 25 insertions(+), 22 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index dc2b5e6a9659..57904b3b18dc 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2304,7 +2304,7 @@ static void stable_tree_append(struct ksm_rmap_item *rmap_item,
* @page: the page that we are searching identical page to.
* @rmap_item: the reverse mapping into the virtual address of this page
*/
-static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_item)
+static void cmp_and_merge_page(struct folio *folio, struct ksm_rmap_item *rmap_item)
{
struct mm_struct *mm = rmap_item->mm;
struct ksm_rmap_item *tree_rmap_item;
@@ -2314,9 +2314,7 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
unsigned int checksum;
int err;
bool max_page_sharing_bypass = false;
- struct folio *folio;

- folio = page_folio(page);
stable_node = folio_stable_node(folio);
if (stable_node) {
if (stable_node->head != &migrate_nodes &&
@@ -2518,12 +2516,12 @@ static unsigned int skip_age(rmap_age_t age)
}

/*
- * Determines if a page should be skipped for the current scan.
+ * Determines if a folio should be skipped for the current scan.
*
- * @page: page to check
- * @rmap_item: associated rmap_item of page
+ * @folio: folio to check
+ * @rmap_item: associated rmap_item of folio
*/
-static bool should_skip_rmap_item(struct page *page,
+static bool should_skip_rmap_item(struct folio *folio,
struct ksm_rmap_item *rmap_item)
{
rmap_age_t age;
@@ -2536,7 +2534,7 @@ static bool should_skip_rmap_item(struct page *page,
* will essentially ignore them, but we still have to process them
* properly.
*/
- if (PageKsm(page))
+ if (folio_test_ksm(folio))
return false;

age = rmap_item->age;
@@ -2566,7 +2564,7 @@ static bool should_skip_rmap_item(struct page *page,
return true;
}

-static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
+static struct ksm_rmap_item *scan_get_next_rmap_item(struct folio **folio)
{
struct mm_struct *mm;
struct ksm_mm_slot *mm_slot;
@@ -2655,36 +2653,41 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
ksm_scan.address = vma->vm_end;

while (ksm_scan.address < vma->vm_end) {
+ struct page *page;
+
if (ksm_test_exit(mm))
break;
- *page = follow_page(vma, ksm_scan.address, FOLL_GET);
- if (IS_ERR_OR_NULL(*page)) {
+ page = follow_page(vma, ksm_scan.address, FOLL_GET);
+ if (IS_ERR_OR_NULL(page)) {
ksm_scan.address += PAGE_SIZE;
cond_resched();
continue;
}

- VM_WARN_ON(PageTail(*page));
- nr = compound_nr(*page);
- if (is_zone_device_page(*page))
+ *folio = page_folio(page);
+ VM_WARN_ON(PageTail(page));
+ nr = folio_nr_pages(*folio);
+
+ if (folio_is_zone_device(*folio))
goto next_page;
- if (PageAnon(*page)) {
+
+ if (folio_test_anon(*folio)) {
rmap_item = get_next_rmap_item(mm_slot,
ksm_scan.rmap_list, ksm_scan.address);
if (rmap_item) {
ksm_scan.rmap_list = &rmap_item->rmap_list;

- if (should_skip_rmap_item(*page, rmap_item))
+ if (should_skip_rmap_item(*folio, rmap_item))
goto next_page;

ksm_scan.address += nr * PAGE_SIZE;
} else
- put_page(*page);
+ folio_put(*folio);
mmap_read_unlock(mm);
return rmap_item;
}
next_page:
- put_page(*page);
+ folio_put(*folio);
ksm_scan.address += nr * PAGE_SIZE;
cond_resched();
}
@@ -2755,16 +2758,16 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
static void ksm_do_scan(unsigned int scan_npages)
{
struct ksm_rmap_item *rmap_item;
- struct page *page;
+ struct folio *folio;
unsigned int npages = scan_npages;

while (npages-- && likely(!freezing(current))) {
cond_resched();
- rmap_item = scan_get_next_rmap_item(&page);
+ rmap_item = scan_get_next_rmap_item(&folio);
if (!rmap_item)
return;
- cmp_and_merge_page(page, rmap_item);
- put_page(page);
+ cmp_and_merge_page(folio, rmap_item);
+ folio_put(folio);
}

ksm_pages_scanned += scan_npages - npages;
--
2.43.0