The patch titled
Subject: mm: move the easily assessable conditions forward
has been added to the -mm mm-unstable branch. Its filename is
mm-remap-unused-subpages-to-shared-zeropage-when-splitting-isolated-thp-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-remap-unused-subpages-to-shared-zeropage-when-splitting-isolated-thp-fix.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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------------------------------------------------------
From: Huan Yang <link@xxxxxxxx>
Subject: mm: move the easily assessable conditions forward
Date: Thu, 15 Aug 2024 16:31:01 +0800
Currently try_to_map_unused_to_zeropage() tries to use shared zero page to
save some memory of sub page.
If forbidding zeropage there is no need to do anything rather than
attempting to assess wthether to use it afterwards.
Link: https://lkml.kernel.org/r/20240815083102.653820-1-link@xxxxxxxx
Signed-off-by: Huan Yang <link@xxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/migrate.c~mm-remap-unused-subpages-to-shared-zeropage-when-splitting-isolated-thp-fix
+++ a/mm/migrate.c
@@ -192,6 +192,9 @@ static bool try_to_map_unused_to_zeropag
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page);
+ if (mm_forbids_zeropage(pvmw->vma->vm_mm))
+ return false;
+
if (PageMlocked(page) || (pvmw->vma->vm_flags & VM_LOCKED))
return false;
@@ -204,7 +207,7 @@ static bool try_to_map_unused_to_zeropag
contains_data = memchr_inv(addr, 0, PAGE_SIZE);
kunmap_local(addr);
- if (contains_data || mm_forbids_zeropage(pvmw->vma->vm_mm))
+ if (contains_data)
return false;
newpte = pte_mkspecial(pfn_pte(my_zero_pfn(pvmw->address),
_
Patches currently in -mm which might be from link@xxxxxxxx are
mm-remap-unused-subpages-to-shared-zeropage-when-splitting-isolated-thp-fix.patch
