On 2023/8/29 10:10, Matthew Wilcox wrote:
On Tue, Aug 29, 2023 at 08:49:31AM +0800, Huang, Ying wrote:
Zi Yan <ziy@xxxxxxxxxx> writes:
On 21 Aug 2023, at 7:56, Kefeng Wang wrote:
Use a folio in migrate_misplaced_page() to save compound_head() calls.
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
mm/migrate.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
LGTM. And a comment below. Reveiwed-by: Zi Yan <ziy@xxxxxxxxxx>
diff --git a/mm/migrate.c b/mm/migrate.c
index 281eafdf8e63..fc728f9a383f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2521,17 +2521,18 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
int node)
{
pg_data_t *pgdat = NODE_DATA(node);
+ struct folio *folio = page_folio(page);
int isolated;
int nr_remaining;
unsigned int nr_succeeded;
LIST_HEAD(migratepages);
- int nr_pages = thp_nr_pages(page);
+ int nr_pages = folio_nr_pages(folio);
/*
* Don't migrate file pages that are mapped in multiple processes
* with execute permissions as they are probably shared libraries.
*/
- if (page_mapcount(page) != 1 && page_is_file_lru(page) &&
+ if (page_mapcount(page) != 1 && folio_is_file_lru(folio) &&
page_mapcount() is not converted, since folio_mapcount() is not equivalent
to page_mapcount(). It can be converted and this function can be converted
to migrate_misplaced_folio() once we have something like folio_num_sharers().
It seems that we can use folio_estimated_sharers() here.
So, funny thing, page_mapcount() was always wrong here. We have two
callers, do_huge_pmd_numa_page() and do_numa_page(). do_numa_page()
has a check for PageCompound() (and /* TODO: handle PTE-mapped THP */).
do_huge_pmd_numa_page() returns pfn_to_page(), after it got the pfn
fromm pmd_pfn(pmd).
for PMD-mapped page，do_huge_pmd_numa_page() return head page
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
page = vm_normal_page_pmd(vma, haddr, pmd);
do_numa_page() only handle base page with PageCompound() check， so we
could use folio_estimated_sharers()， I am not clear why page_mapcount
is wrong here, could you explain more, thank.
That makes folio_estimated_sharers() an improvement, possibly even
a bugfix. Also, we should look at removing the PageCompound() check
in do_numa_page().
Yes, for pte-mapped thp and the large folio numa migrate support, we
need remove the check, we could do it in another patchset.
