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Date: Wed, 20 May 2020 16:22:25 +0800 From: maobibo <maobibo@...ngson.cn> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Jiaxun Yang <jiaxun.yang@...goat.com>, Huacai Chen <chenhc@...ote.com>, Paul Burton <paulburton@...nel.org>, Dmitry Korotin <dkorotin@...ecomp.com>, Philippe Mathieu-Daudé <f4bug@...at.org>, Stafford Horne <shorne@...il.com>, Steven Price <steven.price@....com>, Anshuman Khandual <anshuman.khandual@....com>, linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>, Sergei Shtylyov <sergei.shtylyov@...entembedded.com>, "Maciej W. Rozycki" <macro@....com>, linux-mm@...ck.org, David Hildenbrand <david@...hat.com> Subject: Re: [PATCH v4 3/4] mm/memory.c: Add memory read privilege on page fault handling On 05/20/2020 09:30 AM, Andrew Morton wrote: > On Tue, 19 May 2020 18:03:29 +0800 Bibo Mao <maobibo@...ngson.cn> wrote: > >> Here add pte_sw_mkyoung function to make page readable on MIPS >> platform during page fault handling. This patch improves page >> fault latency about 10% on my MIPS machine with lmbench >> lat_pagefault case. >> >> It is noop function on other arches, there is no negative >> influence on those architectures. >> >> --- a/arch/mips/include/asm/pgtable.h >> +++ b/arch/mips/include/asm/pgtable.h >> @@ -414,6 +414,8 @@ static inline pte_t pte_mkyoung(pte_t pte) >> return pte; >> } >> >> +#define pte_sw_mkyoung pte_mkyoung >> + >> #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT >> static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_HUGE; } >> >> --- a/include/asm-generic/pgtable.h >> +++ b/include/asm-generic/pgtable.h >> @@ -227,6 +227,21 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres >> } >> #endif >> >> +/* >> + * On some architectures hardware does not set page access bit when accessing >> + * memory page, it is responsibilty of software setting this bit. It brings >> + * out extra page fault penalty to track page access bit. For optimization page >> + * access bit can be set during all page fault flow on these arches. >> + * To be differentiate with macro pte_mkyoung, this macro is used on platforms >> + * where software maintains page access bit. >> + */ >> +#ifndef pte_sw_mkyoung >> +static inline pte_t pte_sw_mkyoung(pte_t pte) >> +{ >> + return pte; >> +} >> +#endif > > Yup, that's neat enough. Thanks for making this change. It looks like > all architectures include asm-generic/pgtable.h so that's fine. > > It's conventional to add a > > #define pte_sw_mkyoung pte_sw_mkyoung > > immediately above the #endif there, so we can't try to implement > pte_sw_mkyoung() twice if this header gets included twice. But the > header has #ifndef _ASM_GENERIC_PGTABLE_H around the whole thing so > that should be OK. Sure, will do, and thanks for your kindly help and guidance
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