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    SubjectRe: [PATCH 12/26] mm/nds32: Use general page fault accounting
    Peter Xu <peterx@redhat.com> 於 2020年6月27日 週六 上午6:31寫道:
    >
    > 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;
    >

    Hi Peter,

    Thank you.
    Acked-by: Greentime Hu <green.hu@gmail.com>

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