+ mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs.patch added to mm-new branch

+ mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm: fault in complete folios instead of individual pages for tmpfs
has been added to the -mm mm-new branch.  Its filename is
     mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Subject: mm: fault in complete folios instead of individual pages for tmpfs
Date: Fri, 4 Jul 2025 11:19:26 +0800

After commit acd7ccb284b8 ("mm: shmem: add large folio support for
tmpfs"), tmpfs can also support large folio allocation (not just PMD-sized
large folios).

However, when accessing tmpfs via mmap(), although tmpfs supports large
folios, we still establish mappings at the base page granularity, which is
unreasonable.

We can map multiple consecutive pages of tmpfs folios at once according to
the size of the large folio.  On one hand, this can reduce the overhead of
page faults; on the other hand, it can leverage hardware architecture
optimizations to reduce TLB misses, such as contiguous PTEs on the ARM
architecture.

Moreover, tmpfs mount will use the 'huge=' option to control large folio
allocation explicitly.  So it can be understood that the process's RSS
statistics might increase, and I think this will not cause any obvious
effects for users.

Performance test:
I created a 1G tmpfs file, populated with 64K large folios, and write-accessed it
sequentially via mmap(). I observed a significant performance improvement:

Before the patch:
real	0m0.158s
user	0m0.008s
sys	0m0.150s

After the patch:
real	0m0.021s
user	0m0.004s
sys	0m0.017s

Link: https://lkml.kernel.org/r/440940e78aeb7430c5cc8b6d2088ae98265b9809.1751599072.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/memory.c~mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs
+++ a/mm/memory.c
@@ -5376,10 +5376,10 @@ fallback:
 
 	/*
 	 * Using per-page fault to maintain the uffd semantics, and same
-	 * approach also applies to non-anonymous-shmem faults to avoid
+	 * approach also applies to non shmem/tmpfs faults to avoid
 	 * inflating the RSS of the process.
 	 */
-	if (!vma_is_anon_shmem(vma) || unlikely(userfaultfd_armed(vma)) ||
+	if (!vma_is_shmem(vma) || unlikely(userfaultfd_armed(vma)) ||
 	    unlikely(needs_fallback)) {
 		nr_pages = 1;
 	} else if (nr_pages > 1) {
_

Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are

mm-fix-the-inaccurate-memory-statistics-issue-for-users.patch
selftests-khugepaged-fix-the-shmem-collapse-failure.patch
selftests-mm-add-shmem-collapse-as-a-default-test-item.patch
mm-huge_memory-fix-the-check-for-allowed-huge-orders-in-shmem.patch
khugepaged-allow-khugepaged-to-check-all-anonymous-mthp-orders.patch
khugepaged-kick-khugepaged-for-enabling-none-pmd-sized-mthps.patch
mm-fault-in-complete-folios-instead-of-individual-pages-for-tmpfs.patch