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BACKPORT: mm/memory.c: Add memory read privilege on page fault handling

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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.

Change-Id: Ia5edb3d745d9949cfb0b1316ec5d08dae5761956
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
This commit is contained in:
Bibo Mao 2020-05-27 10:25:19 +08:00 • committed by basamaryan
commit ce18ca1ed3
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3 changed files with 21 additions and 0 deletions
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2
arch/mips/include/asm/pgtable.h
View file

@ -398,6 +398,8 @@ static inline pte_t pte_mkspecial(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; }

16
include/asm-generic/pgtable.h
View file

@ -226,6 +226,22 @@ 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;
}
#define pte_sw_mkyoung pte_sw_mkyoung
#endif
#ifndef pte_savedwrite
#define pte_savedwrite pte_write
#endif

3
mm/memory.c
View file

@ -2539,6 +2539,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
entry = mk_pte(new_page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
/*
* Clear the pte entry and flush it first, before updating the
@ -3214,6 +3215,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
__SetPageUptodate(page);
entry = mk_pte(page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry));
@ -3502,6 +3504,7 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
if (write)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);