The patch titled
Subject: arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS
has been added to the -mm mm-unstable branch. Its filename is
arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.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: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Subject: arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS
Date: Wed, 3 Apr 2024 16:38:00 +0800
The vm_flags of vma already checked under per-VMA lock, if it is a bad
access, directly set fault to VM_FAULT_BADACCESS and handle error, no need
to retry with mmap_lock again, the latency time reduces 34% in 'lat_sig -P
1 prot lat_sig' from lmbench testcase.
Since the page fault is handled under per-VMA lock, count it as a vma lock
event with VMA_LOCK_SUCCESS.
Link: https://lkml.kernel.org/r/20240403083805.1818160-3-wangkefeng.wang@xxxxxxxxxx
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Reviewed-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm64/mm/fault.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/arm64/mm/fault.c~arm64-mm-accelerate-pagefault-when-vm_fault_badaccess
+++ a/arch/arm64/mm/fault.c
@@ -572,7 +572,9 @@ static int __kprobes do_page_fault(unsig
if (!(vma->vm_flags & vm_flags)) {
vma_end_read(vma);
- goto lock_mmap;
+ fault = VM_FAULT_BADACCESS;
+ count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+ goto done;
}
fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
_
Patches currently in -mm which might be from wangkefeng.wang@xxxxxxxxxx are
mm-backing-dev-use-group-allocation-free-of-per-cpu-counters-api.patch
mm-remove-__set_page_dirty_nobuffers.patch
arm64-mm-cleanup-__do_page_fault.patch
arm64-mm-accelerate-pagefault-when-vm_fault_badaccess.patch
arm-mm-accelerate-pagefault-when-vm_fault_badaccess.patch
powerpc-mm-accelerate-pagefault-when-badaccess.patch
riscv-mm-accelerate-pagefault-when-badaccess.patch
s390-mm-accelerate-pagefault-when-badaccess.patch
x86-mm-accelerate-pagefault-when-badaccess.patch
