On Mon, Dec 28, 2015 at 12:05:51PM +0200, Kirill A. Shutemov wrote:
> On Thu, Dec 24, 2015 at 11:20:30AM -0500, Matthew Wilcox wrote:
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 4bf3811..e14634f 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1958,6 +1977,17 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd)
> > return ptl;
> > }
> >
> > +/*
> > + * No scalability reason to split PUD locks yet, but follow the same pattern
> > + * as the PMD locks to make it easier if we have to.
> > + */
>
> I don't think it makes any good unless you convert all other places where
> we use page_table_lock to protect pud table (like __pud_alloc()) to the
> same API.
> I think this would deserve separate patch.
Sure, a separate patch to convert existing users of the PTL. But I
don't think it does any harm to introduce the PUD version of the PMD API.
Maybe with a comment indicating that tere is significant work to be done
in converting existing users to this API?
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 416b129..7328df0 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -1220,9 +1220,27 @@ static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
> > pud = pud_offset(pgd, addr);
> > do {
> > next = pud_addr_end(addr, end);
> > + if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
> > + if (next - addr != HPAGE_PUD_SIZE) {
> > +#ifdef CONFIG_DEBUG_VM
>
> IS_ENABLED(CONFIG_DEBUG_VM) ?
>
> > + if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
> > + pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
> > + __func__, addr, end,
> > + vma->vm_start,
> > + vma->vm_end);
>
> dump_vma(), I guess.
These two issues are copy-and-paste from the existing PMD code. I'm happy
to update the PMD code to the new-and-improved way of doing things;
I'm just not keen to have the PMD and PUD code diverge unnecessarily.
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