linux-kernel - Re: [PATCH v5 24/25] arm64/mm: __always

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Message-ID: <ZcufFVa7FJRgrEI1@FVFF77S0Q05N.cambridge.arm.com>
Date: Tue, 13 Feb 2024 16:55:49 +0000
From: Mark Rutland <mark.rutland@....com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
	Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matthew Wilcox <willy@...radead.org>,
	David Hildenbrand <david@...hat.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	John Hubbard <jhubbard@...dia.com>, Zi Yan <ziy@...dia.com>,
	Barry Song <21cnbao@...il.com>,
	Alistair Popple <apopple@...dia.com>,
	Yang Shi <shy828301@...il.com>, Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 24/25] arm64/mm: __always_inline to improve fork() perf

On Fri, Feb 02, 2024 at 08:07:55AM +0000, Ryan Roberts wrote:
> As set_ptes() and wrprotect_ptes() become a bit more complex, the
> compiler may choose not to inline them. But this is critical for fork()
> performance. So mark the functions, along with contpte_try_unfold()
> which is called by them, as __always_inline. This is worth ~1% on the
> fork() microbenchmark with order-0 folios (the common case).
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>

I have no strong feelings either way on this, so:

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/include/asm/pgtable.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 353ea67b5d75..cdc310880a3b 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -1213,8 +1213,8 @@ extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma,
>  				unsigned long addr, pte_t *ptep,
>  				pte_t entry, int dirty);
>  
> -static inline void contpte_try_unfold(struct mm_struct *mm, unsigned long addr,
> -					pte_t *ptep, pte_t pte)
> +static __always_inline void contpte_try_unfold(struct mm_struct *mm,
> +				unsigned long addr, pte_t *ptep, pte_t pte)
>  {
>  	if (unlikely(pte_valid_cont(pte)))
>  		__contpte_try_unfold(mm, addr, ptep, pte);
> @@ -1279,7 +1279,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte)
>  }
>  
>  #define set_ptes set_ptes
> -static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> +static __always_inline void set_ptes(struct mm_struct *mm, unsigned long addr,
>  				pte_t *ptep, pte_t pte, unsigned int nr)
>  {
>  	pte = pte_mknoncont(pte);
> @@ -1361,8 +1361,8 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>  }
>  
>  #define wrprotect_ptes wrprotect_ptes
> -static inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
> -				pte_t *ptep, unsigned int nr)
> +static __always_inline void wrprotect_ptes(struct mm_struct *mm,
> +				unsigned long addr, pte_t *ptep, unsigned int nr)
>  {
>  	if (likely(nr == 1)) {
>  		/*
> -- 
> 2.25.1
>