7fccfc00c0
When unmapping N pages (e.g. shared memory) the amount of TLB flushes done can be (N*PAGE_SIZE/ZAP_BLOCK_SIZE)*N although it should be N at maximum. With PREEMPT kernel ZAP_BLOCK_SIZE is 8 pages, so there is a noticeable performance penalty when unmapping a large VMA and the system is spending its time in flush_tlb_range(). The problem is that tlb_end_vma() is always flushing the full VMA range. The subrange that needs to be flushed can be calculated by tlb_remove_tlb_entry(). This approach was suggested by Hugh Dickins, and is also used by other arches. The speed increase is roughly 3x for 8M mappings and for larger mappings even more. Signed-off-by: Aaro Koskinen <Aaro.Koskinen@nokia.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
112 lines
2.7 KiB
C
112 lines
2.7 KiB
C
/*
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* arch/arm/include/asm/tlb.h
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*
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* Copyright (C) 2002 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Experimentation shows that on a StrongARM, it appears to be faster
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* to use the "invalidate whole tlb" rather than "invalidate single
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* tlb" for this.
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*
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* This appears true for both the process fork+exit case, as well as
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* the munmap-large-area case.
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*/
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#ifndef __ASMARM_TLB_H
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#define __ASMARM_TLB_H
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#ifndef CONFIG_MMU
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#include <linux/pagemap.h>
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#include <asm-generic/tlb.h>
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#else /* !CONFIG_MMU */
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#include <asm/pgalloc.h>
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/*
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* TLB handling. This allows us to remove pages from the page
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* tables, and efficiently handle the TLB issues.
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*/
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struct mmu_gather {
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struct mm_struct *mm;
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unsigned int fullmm;
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unsigned long range_start;
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unsigned long range_end;
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};
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DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
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static inline struct mmu_gather *
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tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
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{
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struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
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tlb->mm = mm;
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tlb->fullmm = full_mm_flush;
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return tlb;
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}
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static inline void
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tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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{
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if (tlb->fullmm)
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flush_tlb_mm(tlb->mm);
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/* keep the page table cache within bounds */
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check_pgt_cache();
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put_cpu_var(mmu_gathers);
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}
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/*
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* Memorize the range for the TLB flush.
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*/
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static inline void
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tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep, unsigned long addr)
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{
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if (!tlb->fullmm) {
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if (addr < tlb->range_start)
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tlb->range_start = addr;
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if (addr + PAGE_SIZE > tlb->range_end)
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tlb->range_end = addr + PAGE_SIZE;
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}
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}
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/*
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* In the case of tlb vma handling, we can optimise these away in the
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* case where we're doing a full MM flush. When we're doing a munmap,
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* the vmas are adjusted to only cover the region to be torn down.
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*/
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static inline void
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tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
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{
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if (!tlb->fullmm) {
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flush_cache_range(vma, vma->vm_start, vma->vm_end);
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tlb->range_start = TASK_SIZE;
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tlb->range_end = 0;
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}
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}
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static inline void
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tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
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{
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if (!tlb->fullmm && tlb->range_end > 0)
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flush_tlb_range(vma, tlb->range_start, tlb->range_end);
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}
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#define tlb_remove_page(tlb,page) free_page_and_swap_cache(page)
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#define pte_free_tlb(tlb, ptep) pte_free((tlb)->mm, ptep)
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#define pmd_free_tlb(tlb, pmdp) pmd_free((tlb)->mm, pmdp)
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#define tlb_migrate_finish(mm) do { } while (0)
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#endif /* CONFIG_MMU */
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#endif
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