The patch titled
Subject: mm/numa: no task_numa_fault() call if PTE is changed
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-numa-no-task_numa_fault-call-if-pte-is-changed.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-numa-no-task_numa_fault-call-if-pte-is-changed.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zi Yan <ziy@xxxxxxxxxx>
Subject: mm/numa: no task_numa_fault() call if PTE is changed
Date: Fri, 9 Aug 2024 10:59:04 -0400
When handling a numa page fault, task_numa_fault() should be called by a
process that restores the page table of the faulted folio to avoid
duplicated stats counting. Commit b99a342d4f11 ("NUMA balancing: reduce
TLB flush via delaying mapping on hint page fault") restructured
do_numa_page() and did not avoid task_numa_fault() call in the second page
table check after a numa migration failure. Fix it by making all
!pte_same() return immediately.
This issue can cause task_numa_fault() being called more than necessary
and lead to unexpected numa balancing results (It is hard to tell whether
the issue will cause positive or negative performance impact due to
duplicated numa fault counting).
Link: https://lkml.kernel.org/r/20240809145906.1513458-2-ziy@xxxxxxxxxx
Fixes: b99a342d4f11 ("NUMA balancing: reduce TLB flush via delaying mapping on hint page fault")
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Reported-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Closes: https://lore.kernel.org/linux-mm/87zfqfw0yw.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 33 ++++++++++++++++-----------------
1 file changed, 16 insertions(+), 17 deletions(-)
--- a/mm/memory.c~mm-numa-no-task_numa_fault-call-if-pte-is-changed
+++ a/mm/memory.c
@@ -5295,7 +5295,7 @@ static vm_fault_t do_numa_page(struct vm
if (unlikely(!pte_same(old_pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
+ return 0;
}
pte = pte_modify(old_pte, vma->vm_page_prot);
@@ -5358,23 +5358,19 @@ static vm_fault_t do_numa_page(struct vm
if (!migrate_misplaced_folio(folio, vma, target_nid)) {
nid = target_nid;
flags |= TNF_MIGRATED;
- } else {
- flags |= TNF_MIGRATE_FAIL;
- vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
- vmf->address, &vmf->ptl);
- if (unlikely(!vmf->pte))
- goto out;
- if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) {
- pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
- }
- goto out_map;
+ task_numa_fault(last_cpupid, nid, nr_pages, flags);
+ return 0;
}
-out:
- if (nid != NUMA_NO_NODE)
- task_numa_fault(last_cpupid, nid, nr_pages, flags);
- return 0;
+ flags |= TNF_MIGRATE_FAIL;
+ vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
+ vmf->address, &vmf->ptl);
+ if (unlikely(!vmf->pte))
+ return 0;
+ if (unlikely(!pte_same(ptep_get(vmf->pte), vmf->orig_pte))) {
+ pte_unmap_unlock(vmf->pte, vmf->ptl);
+ return 0;
+ }
out_map:
/*
* Make it present again, depending on how arch implements
@@ -5387,7 +5383,10 @@ out_map:
numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte,
writable);
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
+
+ if (nid != NUMA_NO_NODE)
+ task_numa_fault(last_cpupid, nid, nr_pages, flags);
+ return 0;
}
static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
_
Patches currently in -mm which might be from ziy@xxxxxxxxxx are
mm-numa-no-task_numa_fault-call-if-pte-is-changed.patch
mm-numa-no-task_numa_fault-call-if-pmd-is-changed.patch
memory-tiering-read-last_cpupid-correctly-in-do_huge_pmd_numa_page.patch
memory-tiering-introduce-folio_use_access_time-check.patch
memory-tiering-count-pgpromote_success-when-mem-tiering-is-enabled.patch
