On Wed, Apr 08, 2009 at 03:58:16AM +0800, Ying Han wrote:
> On Tue, Apr 7, 2009 at 12:17 AM, Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote:
> > VM_FAULT_RETRY does make major/minor faults accounting a bit twisted..
> >
> > Cc: Ying Han <yinghan@xxxxxxxxxx>
> > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> > ---
> > arch/x86/mm/fault.c | 2 ++
> > mm/memory.c | 22 ++++++++++++++--------
> > 2 files changed, 16 insertions(+), 8 deletions(-)
> >
> > --- mm.orig/arch/x86/mm/fault.c
> > +++ mm/arch/x86/mm/fault.c
> > @@ -1160,6 +1160,8 @@ good_area:
> > if (fault & VM_FAULT_RETRY) {
> > if (retry_flag) {
> > retry_flag = 0;
> > + tsk->maj_flt++;
> > + tsk->min_flt--;
> > goto retry;
> > }
> > BUG();
> sorry, little bit confuse here. are we assuming the retry path will
> return min_flt as always?
Sure - except for some really exceptional ftruncate cases.
The page was there ready, and we'll retry immediately.
maj_flt/min_flt are not _exact_ numbers by their nature, so 99.9%
accuracy shall be fine.
Thanks,
Fengguang
> > --- mm.orig/mm/memory.c
> > +++ mm/mm/memory.c
> > @@ -2882,26 +2882,32 @@ int handle_mm_fault(struct mm_struct *mm
> > pud_t *pud;
> > pmd_t *pmd;
> > pte_t *pte;
> > + int ret;
> >
> > __set_current_state(TASK_RUNNING);
> >
> > - count_vm_event(PGFAULT);
> > -
> > - if (unlikely(is_vm_hugetlb_page(vma)))
> > - return hugetlb_fault(mm, vma, address, write_access);
> > + if (unlikely(is_vm_hugetlb_page(vma))) {
> > + ret = hugetlb_fault(mm, vma, address, write_access);
> > + goto out;
> > + }
> >
> > + ret = VM_FAULT_OOM;
> > pgd = pgd_offset(mm, address);
> > pud = pud_alloc(mm, pgd, address);
> > if (!pud)
> > - return VM_FAULT_OOM;
> > + goto out;
> > pmd = pmd_alloc(mm, pud, address);
> > if (!pmd)
> > - return VM_FAULT_OOM;
> > + goto out;
> > pte = pte_alloc_map(mm, pmd, address);
> > if (!pte)
> > - return VM_FAULT_OOM;
> > + goto out;
> >
> > - return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
> > + ret = handle_pte_fault(mm, vma, address, pte, pmd, write_access);
> > +out:
> > + if (!(ret & VM_FAULT_RETRY))
> > + count_vm_event(PGFAULT);
> > + return ret;
> > }
> >
> > #ifndef __PAGETABLE_PUD_FOLDED
> >
> > --
> >
> >
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