mirror of https://gitee.com/openkylin/linux.git
[ARM] 5450/1: Flush only the needed range when unmapping a VMA
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>
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@ -36,6 +36,8 @@
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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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@ -63,7 +65,19 @@ tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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put_cpu_var(mmu_gathers);
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}
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#define tlb_remove_tlb_entry(tlb,ptep,address) do { } while (0)
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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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@ -73,15 +87,18 @@ tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
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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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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)
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flush_tlb_range(vma, vma->vm_start, vma->vm_end);
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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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