The patch titled
Subject: mm: khugepaged: avoid pointless allocation for "struct mm_slot"
has been added to the -mm mm-unstable branch. Its filename is
mm-khugepaged-avoid-pointless-allocation-for-struct-mm_slot.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-avoid-pointless-allocation-for-struct-mm_slot.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: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
Subject: mm: khugepaged: avoid pointless allocation for "struct mm_slot"
Date: Wed, 31 May 2023 17:58:17 +0800
In __khugepaged_enter(), if "mm->flags" with MMF_VM_HUGEPAGE bit is set,
the "mm_slot" will be released and return, so we can call mm_slot_alloc()
after test_and_set_bit().
Link: https://lkml.kernel.org/r/20230531095817.11012-1-xhao@xxxxxxxxxxxxxxxxx
Signed-off-by: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
--- a/mm/khugepaged.c~mm-khugepaged-avoid-pointless-allocation-for-struct-mm_slot
+++ a/mm/khugepaged.c
@@ -422,19 +422,17 @@ void __khugepaged_enter(struct mm_struct
struct mm_slot *slot;
int wakeup;
+ /* __khugepaged_exit() must not run from under us */
+ VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm);
+ if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags)))
+ return;
+
mm_slot = mm_slot_alloc(mm_slot_cache);
if (!mm_slot)
return;
slot = &mm_slot->slot;
- /* __khugepaged_exit() must not run from under us */
- VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm);
- if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
- mm_slot_free(mm_slot_cache, mm_slot);
- return;
- }
-
spin_lock(&khugepaged_mm_lock);
mm_slot_insert(mm_slots_hash, mm, slot);
/*
_
Patches currently in -mm which might be from xhao@xxxxxxxxxxxxxxxxx are
mm-khugepaged-avoid-pointless-allocation-for-struct-mm_slot.patch
