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39dde65c99
Following up with the work on shared page table done by Dave McCracken. This set of patch target shared page table for hugetlb memory only. The shared page table is particular useful in the situation of large number of independent processes sharing large shared memory segments. In the normal page case, the amount of memory saved from process' page table is quite significant. For hugetlb, the saving on page table memory is not the primary objective (as hugetlb itself already cuts down page table overhead significantly), instead, the purpose of using shared page table on hugetlb is to allow faster TLB refill and smaller cache pollution upon TLB miss. With PT sharing, pte entries are shared among hundreds of processes, the cache consumption used by all the page table is smaller and in return, application gets much higher cache hit ratio. One other effect is that cache hit ratio with hardware page walker hitting on pte in cache will be higher and this helps to reduce tlb miss latency. These two effects contribute to higher application performance. Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: Dave McCracken <dmccr@us.ibm.com> Cc: William Lee Irwin III <wli@holomorphy.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Gibson <david@gibson.dropbear.id.au> Cc: Adam Litke <agl@us.ibm.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
87 lines
1.5 KiB
C
87 lines
1.5 KiB
C
/*
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* arch/sh/mm/hugetlbpage.c
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*
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* SuperH HugeTLB page support.
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*
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* Cloned from sparc64 by Paul Mundt.
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*
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* Copyright (C) 2002, 2003 David S. Miller (davem@redhat.com)
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*/
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/hugetlb.h>
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#include <linux/pagemap.h>
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#include <linux/smp_lock.h>
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#include <linux/slab.h>
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#include <linux/sysctl.h>
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#include <asm/mman.h>
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#include <asm/pgalloc.h>
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#include <asm/tlb.h>
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#include <asm/tlbflush.h>
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#include <asm/cacheflush.h>
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pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte = NULL;
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pgd = pgd_offset(mm, addr);
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if (pgd) {
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pud = pud_alloc(mm, pgd, addr);
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if (pud) {
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pmd = pmd_alloc(mm, pud, addr);
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if (pmd)
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pte = pte_alloc_map(mm, pmd, addr);
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}
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}
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return pte;
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}
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pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte = NULL;
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pgd = pgd_offset(mm, addr);
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if (pgd) {
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pud = pud_offset(pgd, addr);
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if (pud) {
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pmd = pmd_offset(pud, addr);
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if (pmd)
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pte = pte_offset_map(pmd, addr);
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}
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}
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return pte;
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}
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int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
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{
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return 0;
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}
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struct page *follow_huge_addr(struct mm_struct *mm,
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unsigned long address, int write)
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{
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return ERR_PTR(-EINVAL);
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}
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int pmd_huge(pmd_t pmd)
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{
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return 0;
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}
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struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
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pmd_t *pmd, int write)
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{
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return NULL;
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}
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