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From: Will Deacon <will@kernel.org>
To: Peter Xu <peterx@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Gerald Schaefer <gerald.schaefer@de.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 06/25] mm/arm64: Use mm_fault_accounting()
Date: Tue, 16 Jun 2020 08:43:08 +0100	[thread overview]
Message-ID: <20200616074307.GA1637@willie-the-truck> (raw)
In-Reply-To: <20200615221607.7764-7-peterx@redhat.com>

On Mon, Jun 15, 2020 at 06:15:48PM -0400, Peter Xu wrote:
> Use the new mm_fault_accounting() helper for page fault accounting.
> 
> CC: Catalin Marinas <catalin.marinas@arm.com>
> CC: Will Deacon <will@kernel.org>
> CC: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  arch/arm64/mm/fault.c | 17 ++---------------
>  1 file changed, 2 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index c9cedc0432d2..09af7d7a60ec 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -484,8 +484,6 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
>  					 addr, esr, regs);
>  	}
>  
> -	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
> -
>  	/*
>  	 * As per x86, we may deadlock here. However, since the kernel only
>  	 * validly references user space from well defined areas of the code,
> @@ -535,20 +533,9 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
>  			      VM_FAULT_BADACCESS)))) {
>  		/*
>  		 * Major/minor page fault accounting is only done
> -		 * once. If we go through a retry, it is extremely
> -		 * likely that the page will be found in page cache at
> -		 * that point.
> +		 * once.
>  		 */
> -		if (major) {
> -			current->maj_flt++;
> -			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs,
> -				      addr);
> -		} else {
> -			current->min_flt++;
> -			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs,
> -				      addr);
> -		}
> -
> +		mm_fault_accounting(current, regs, address, major);

Please can you explain why it's ok to move the PERF_COUNT_SW_PAGE_FAULTS
update like this? Seems like a user-visible change to me, so some
justification would really help.

Will

  reply	other threads:[~2020-06-16  7:43 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-15 22:15 [PATCH 00/25] mm: Page fault accounting cleanups Peter Xu
2020-06-15 22:15 ` [PATCH 01/25] mm/um: Fix extra accounting for page fault retries Peter Xu
2020-06-15 22:15 ` [PATCH 02/25] mm: Introduce mm_fault_accounting() Peter Xu
2020-06-15 22:32   ` Linus Torvalds
2020-06-15 23:19     ` Peter Xu
2020-06-16 19:00       ` Andrew Morton
2020-06-17 16:26         ` Peter Xu
2020-06-15 22:15 ` [PATCH 03/25] mm/alpha: Use mm_fault_accounting() Peter Xu
2020-06-15 22:15 ` [PATCH 04/25] mm/arc: " Peter Xu
2020-06-15 22:15 ` [PATCH 05/25] mm/arm: " Peter Xu
2020-06-15 22:15 ` [PATCH 06/25] mm/arm64: " Peter Xu
2020-06-16  7:43   ` Will Deacon [this message]
2020-06-16 15:59     ` Peter Xu
2020-06-15 22:15 ` [PATCH 07/25] mm/csky: " Peter Xu
2020-06-17  7:04   ` Guo Ren
2020-06-17 15:49     ` Peter Xu
2020-06-17 17:53       ` Linus Torvalds
2020-06-17 19:58         ` Peter Xu
2020-06-17 20:15           ` Linus Torvalds
2020-06-18 14:38             ` Peter Xu
2020-06-18 17:15               ` Linus Torvalds
2020-06-18 21:24                 ` Peter Xu
2020-06-18 22:28                   ` Peter Xu
2020-06-18 22:59                     ` Linus Torvalds
2020-06-15 22:15 ` [PATCH 08/25] mm/hexagon: " Peter Xu
2020-06-15 22:15 ` [PATCH 09/25] mm/ia64: " Peter Xu
2020-06-15 22:15 ` [PATCH 10/25] mm/m68k: " Peter Xu
2020-06-15 22:15 ` [PATCH 11/25] mm/microblaze: " Peter Xu
2020-06-15 22:15 ` [PATCH 12/25] mm/mips: " Peter Xu
2020-06-15 22:15 ` [PATCH 13/25] mm/nds32: " Peter Xu
2020-06-17  1:05   ` Greentime Hu
2020-06-15 22:15 ` [PATCH 14/25] mm/nios2: " Peter Xu
2020-06-15 22:15 ` [PATCH 15/25] mm/openrisc: " Peter Xu
2020-06-16 18:11   ` Stafford Horne
2020-06-15 22:15 ` [PATCH 16/25] mm/parisc: " Peter Xu
2020-06-15 22:15 ` [PATCH 17/25] mm/powerpc: " Peter Xu
2020-06-15 22:16 ` [PATCH 18/25] mm/riscv: " Peter Xu
2020-06-18 23:49   ` Palmer Dabbelt
2020-06-19  0:12     ` Peter Xu
2020-06-15 22:23 ` [PATCH 19/25] mm/s390: " Peter Xu
2020-06-16 15:59   ` Alexander Gordeev
2020-06-16 16:35     ` Peter Xu
2020-06-17  6:19       ` Christian Borntraeger
2020-06-17 16:06         ` Peter Xu
2020-06-17 16:14           ` Christian Borntraeger
2020-06-17 16:44             ` Peter Xu
2020-06-15 22:23 ` [PATCH 20/25] mm/sh: " Peter Xu
2020-07-20 21:25   ` Rich Felker
2020-07-20 22:05     ` Peter Xu
2020-06-15 22:23 ` [PATCH 21/25] mm/sparc32: " Peter Xu
2020-06-15 22:23 ` [PATCH 22/25] mm/sparc64: " Peter Xu
2020-06-15 22:23 ` [PATCH 23/25] mm/unicore32: " Peter Xu
2020-06-15 22:23 ` [PATCH 24/25] mm/x86: " Peter Xu
2020-06-15 22:23 ` [PATCH 25/25] mm/xtensa: " Peter Xu
2020-06-15 23:13   ` Max Filippov
2020-06-16 18:55 ` [PATCH 00/25] mm: Page fault accounting cleanups Linus Torvalds
2020-06-16 21:03   ` Peter Xu
2020-06-17  0:55   ` Michael Ellerman
2020-06-17  8:04     ` Will Deacon
2020-06-17 16:10       ` Peter Xu

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