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From: Palmer Dabbelt <palmer@dabbelt.com>
To: peterx@redhat.com
Cc: linux-kernel@vger.kernel.org, gerald.schaefer@de.ibm.com,
	akpm@linux-foundation.org, peterx@redhat.com,
	Linus Torvalds <torvalds@linux-foundation.org>,
	aarcange@redhat.com, Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org
Subject: Re: [PATCH 18/25] mm/riscv: Use mm_fault_accounting()
Date: Thu, 18 Jun 2020 16:49:23 -0700 (PDT)	[thread overview]
Message-ID: <mhng-261b69ba-d08f-4560-9c69-f4ece64a7729@palmerdabbelt-glaptop1> (raw)
In-Reply-To: <20200615221607.7764-19-peterx@redhat.com>

On Mon, 15 Jun 2020 15:16:00 PDT (-0700), peterx@redhat.com wrote:
> Use the new mm_fault_accounting() helper for page fault accounting.
>
> Avoid doing page fault accounting multiple times if the page fault is retried.
>
> CC: Paul Walmsley <paul.walmsley@sifive.com>
> CC: Palmer Dabbelt <palmer@dabbelt.com>
> CC: Albert Ou <aou@eecs.berkeley.edu>
> CC: linux-riscv@lists.infradead.org
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  arch/riscv/mm/fault.c | 21 +++------------------
>  1 file changed, 3 insertions(+), 18 deletions(-)
>
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index be84e32adc4c..9262338614d1 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -30,7 +30,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  	struct vm_area_struct *vma;
>  	struct mm_struct *mm;
>  	unsigned long addr, cause;
> -	unsigned int flags = FAULT_FLAG_DEFAULT;
> +	unsigned int flags = FAULT_FLAG_DEFAULT, major = 0;
>  	int code = SEGV_MAPERR;
>  	vm_fault_t fault;
>
> @@ -65,9 +65,6 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>
>  	if (user_mode(regs))
>  		flags |= FAULT_FLAG_USER;
> -
> -	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
> -
>  retry:
>  	down_read(&mm->mmap_sem);
>  	vma = find_vma(mm, addr);
> @@ -111,6 +108,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  	 * the fault.
>  	 */
>  	fault = handle_mm_fault(vma, addr, flags);
> +	major |= fault & VM_FAULT_MAJOR;
>
>  	/*
>  	 * If we need to retry but a fatal signal is pending, handle the
> @@ -128,21 +126,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  		BUG();
>  	}
>
> -	/*
> -	 * Major/minor page fault accounting is only done on the
> -	 * initial attempt. If we go through a retry, it is extremely
> -	 * likely that the page will be found in page cache at that point.
> -	 */
>  	if (flags & FAULT_FLAG_ALLOW_RETRY) {
> -		if (fault & VM_FAULT_MAJOR) {
> -			tsk->maj_flt++;
> -			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
> -				      1, regs, addr);
> -		} else {
> -			tsk->min_flt++;
> -			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
> -				      1, regs, addr);
> -		}
>  		if (fault & VM_FAULT_RETRY) {
>  			flags |= FAULT_FLAG_TRIED;
>
> @@ -156,6 +140,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>  	}
>
>  	up_read(&mm->mmap_sem);
> +	mm_fault_accounting(tsk, regs, addr, major);
>  	return;
>
>  	/*

AFAICT this changes the behavior of the perf event: it used to count any fault,
whereas now it only counts those that succeed successfully.  If everyone else
is doing it that way then I'm happy to change us over, but this definately
isn't just avoiding retries.

  reply	other threads:[~2020-06-18 23:49 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
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 [this message]
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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