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    Subject[PATH v2 3/5] x86/tlb: fall back to flush all when meet a THP large page
    Date
    We don't need to flush large pages by PAGE_SIZE step, that just waste
    time. and actually, large page don't need 'invlpg' optimizing according
    to our macro benchmark. So, just flush whole TLB is enough for them.

    The following result is tested on a 2CPU * 4cores * 2HT NHM EP machine,
    with THP 'always' setting.

    Multi-thread testing, '-t' paramter is thread number:
    without this patch with this patch
    ./mprotect -t 1 14ns 13ns
    ./mprotect -t 2 13ns 13ns
    ./mprotect -t 4 12ns 11ns
    ./mprotect -t 8 14ns 10ns
    ./mprotect -t 16 28ns 28ns
    ./mprotect -t 32 54ns 52ns
    ./mprotect -t 128 200ns 200ns

    Signed-off-by: Alex Shi <alex.shi@intel.com>
    ---
    arch/x86/mm/tlb.c | 27 +++++++++++++++++++++++++++
    1 files changed, 27 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
    index c4e694d..4f709e6 100644
    --- a/arch/x86/mm/tlb.c
    +++ b/arch/x86/mm/tlb.c
    @@ -316,12 +316,35 @@ void flush_tlb_mm(struct mm_struct *mm)

    #define FLUSHALL_BAR 16

    +static inline int has_large_page(struct mm_struct *mm,
    + unsigned long start, unsigned long end)
    +{
    + pgd_t *pgd;
    + pud_t *pud;
    + pmd_t *pmd;
    + unsigned long addr;
    + for (addr = start; addr <= end; addr += HPAGE_SIZE) {
    + pgd = pgd_offset(mm, addr);
    + if (likely(!pgd_none(*pgd))) {
    + pud = pud_offset(pgd, addr);
    + if (likely(!pud_none(*pud))) {
    + pmd = pmd_offset(pud, addr);
    + if (likely(!pmd_none(*pmd)))
    + if (pmd_large(*pmd))
    + return 1;
    + }
    + }
    + }
    + return 0;
    +}
    +
    void flush_tlb_range(struct vm_area_struct *vma,
    unsigned long start, unsigned long end)
    {
    struct mm_struct *mm;

    if (!cpu_has_invlpg || vma->vm_flags & VM_HUGETLB) {
    +flush_all:
    flush_tlb_mm(vma->vm_mm);
    return;
    }
    @@ -344,6 +367,10 @@ void flush_tlb_range(struct vm_area_struct *vma,
    if ((end - start)/PAGE_SIZE > act_entries/FLUSHALL_BAR)
    local_flush_tlb();
    else {
    + if (has_large_page(mm, start, end)) {
    + preempt_enable();
    + goto flush_all;
    + }
    for (addr = start; addr <= end;
    addr += PAGE_SIZE)
    __flush_tlb_single(addr);
    --
    1.7.0.1


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