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    Subject[PATCH 12/26] mm/nds32: Use general page fault accounting
    Date
    Use the general page fault accounting by passing regs into handle_mm_fault().
    It naturally solve the issue of multiple page fault accounting when page fault
    retry happened.

    Fix PERF_COUNT_SW_PAGE_FAULTS perf event manually for page fault retries, by
    moving it before taking mmap_sem.

    CC: Nick Hu <nickhu@andestech.com>
    CC: Greentime Hu <green.hu@gmail.com>
    CC: Vincent Chen <deanbo422@gmail.com>
    Signed-off-by: Peter Xu <peterx@redhat.com>
    ---
    arch/nds32/mm/fault.c | 19 +++----------------
    1 file changed, 3 insertions(+), 16 deletions(-)

    diff --git a/arch/nds32/mm/fault.c b/arch/nds32/mm/fault.c
    index 22527129025c..e7344440623c 100644
    --- a/arch/nds32/mm/fault.c
    +++ b/arch/nds32/mm/fault.c
    @@ -122,6 +122,8 @@ void do_page_fault(unsigned long entry, unsigned long addr,
    if (unlikely(faulthandler_disabled() || !mm))
    goto no_context;

    + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
    +
    /*
    * As per x86, we may deadlock here. However, since the kernel only
    * validly references user space from well defined areas of the code,
    @@ -207,7 +209,7 @@ void do_page_fault(unsigned long entry, unsigned long addr,
    * the fault.
    */

    - fault = handle_mm_fault(vma, addr, flags, NULL);
    + fault = handle_mm_fault(vma, addr, flags, regs);

    /*
    * If we need to retry but a fatal signal is pending, handle the
    @@ -229,22 +231,7 @@ void do_page_fault(unsigned long entry, unsigned long addr,
    goto bad_area;
    }

    - /*
    - * Major/minor page fault accounting is only done on the initial
    - * attempt. If we go through a retry, it is extremely likely that the
    - * page will be found in page cache at that point.
    - */
    - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
    if (flags & FAULT_FLAG_ALLOW_RETRY) {
    - if (fault & VM_FAULT_MAJOR) {
    - tsk->maj_flt++;
    - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
    - 1, regs, addr);
    - } else {
    - tsk->min_flt++;
    - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
    - 1, regs, addr);
    - }
    if (fault & VM_FAULT_RETRY) {
    flags |= FAULT_FLAG_TRIED;

    --
    2.26.2
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