From: Catalin Marinas <catalin.marinas@arm•com>
To: Kefeng Wang <wangkefeng.wang@huawei•com>
Cc: x86@kernel•org, Albert Ou <aou@eecs•berkeley.edu>,
linux-s390@vger•kernel.org, Peter Zijlstra <peterz@infradead•org>,
Dave Hansen <dave.hansen@linux•intel.com>,
Russell King <linux@armlinux•org.uk>,
surenb@google•com, linuxppc-dev@lists•ozlabs.org,
linux-riscv@lists•infradead.org,
Palmer Dabbelt <palmer@dabbelt•com>,
Nicholas Piggin <npiggin@gmail•com>,
Andy Lutomirski <luto@kernel•org>,
Paul Walmsley <paul.walmsley@sifive•com>,
akpm@linux-foundation•org,
Gerald Schaefer <gerald.schaefer@linux•ibm.com>,
Will Deacon <will@kernel•org>,
Alexander Gordeev <agordeev@linux•ibm.com>,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH 2/7] arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS
Date: Wed, 3 Apr 2024 19:32:25 +0100 [thread overview]
Message-ID: <Zg2guRk4hTIdf_Tm@arm.com> (raw)
In-Reply-To: <20240402075142.196265-3-wangkefeng.wang@huawei.com>
On Tue, Apr 02, 2024 at 03:51:37PM +0800, Kefeng Wang wrote:
> 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 lock_mm_and_find_vma() and check vm_flags again, the latency
> time reduce 34% in lmbench 'lat_sig -P 1 prot lat_sig'.
>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei•com>
> ---
> arch/arm64/mm/fault.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 9bb9f395351a..405f9aa831bd 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -572,7 +572,9 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
>
> 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)))
I think this makes sense. A concurrent modification of vma->vm_flags
(e.g. mprotect()) would do a vma_start_write(), so no need to recheck
again with the mmap lock held.
Reviewed-by: Catalin Marinas <catalin.marinas@arm•com>
next prev parent reply other threads:[~2024-04-03 18:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-02 7:51 [PATCH 0/7] arch/mm/fault: accelerate pagefault when badaccess Kefeng Wang
2024-04-02 7:51 ` [PATCH 1/7] arm64: mm: cleanup __do_page_fault() Kefeng Wang
2024-04-03 5:11 ` Suren Baghdasaryan
2024-04-03 18:24 ` Catalin Marinas
2024-04-02 7:51 ` [PATCH 2/7] arm64: mm: accelerate pagefault when VM_FAULT_BADACCESS Kefeng Wang
2024-04-03 5:19 ` Suren Baghdasaryan
2024-04-03 5:30 ` Suren Baghdasaryan
2024-04-03 6:13 ` Kefeng Wang
2024-04-03 18:32 ` Catalin Marinas [this message]
2024-04-02 7:51 ` [PATCH 3/7] arm: " Kefeng Wang
2024-04-03 5:30 ` Suren Baghdasaryan
2024-04-02 7:51 ` [PATCH 4/7] powerpc: mm: accelerate pagefault when badaccess Kefeng Wang
2024-04-03 5:34 ` Suren Baghdasaryan
2024-04-02 7:51 ` [PATCH 5/7] riscv: " Kefeng Wang
2024-04-03 5:37 ` Suren Baghdasaryan
2024-04-02 7:51 ` [PATCH 6/7] s390: " Kefeng Wang
2024-04-02 7:51 ` [PATCH 7/7] x86: " Kefeng Wang
2024-04-03 5:59 ` Suren Baghdasaryan
2024-04-03 7:58 ` Kefeng Wang
2024-04-03 14:23 ` Suren Baghdasaryan
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