The patch titled
Subject: mm/numa: no task_numa_fault() call if page table is changed
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-numa-no-task_numa_fault-call-if-page-table-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-page-table-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 page table is changed
Date: Wed, 7 Aug 2024 14:47:29 -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 do_huge_pmd_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()/!pmd_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/20240807184730.1266736-1-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/
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 5 +++--
mm/memory.c | 5 +++--
2 files changed, 6 insertions(+), 4 deletions(-)
--- a/mm/huge_memory.c~mm-numa-no-task_numa_fault-call-if-page-table-is-changed
+++ a/mm/huge_memory.c
@@ -1738,10 +1738,11 @@ vm_fault_t do_huge_pmd_numa_page(struct
goto out_map;
}
-out:
+count_fault:
if (nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
+out:
return 0;
out_map:
@@ -1753,7 +1754,7 @@ out_map:
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
spin_unlock(vmf->ptl);
- goto out;
+ goto count_fault;
}
/*
--- a/mm/memory.c~mm-numa-no-task_numa_fault-call-if-page-table-is-changed
+++ a/mm/memory.c
@@ -5371,9 +5371,10 @@ static vm_fault_t do_numa_page(struct vm
goto out_map;
}
-out:
+count_fault:
if (nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, nid, nr_pages, flags);
+out:
return 0;
out_map:
/*
@@ -5387,7 +5388,7 @@ out_map:
numa_rebuild_single_mapping(vmf, vma, vmf->address, vmf->pte,
writable);
pte_unmap_unlock(vmf->pte, vmf->ptl);
- goto out;
+ goto count_fault;
}
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-page-table-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
mm-migrate-move-common-code-to-numa_migrate_check-was-numa_migrate_prep.patch
