On Thu, Feb 24, 2011 at 02:43:04PM -0800, Dave Hansen wrote:
> On Tue, 2011-02-22 at 17:52 -0800, Andi Kleen wrote:
> > @@ -2286,6 +2290,9 @@ void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
> > spin_unlock(&mm->page_table_lock);
> > return;
> > }
> > +
> > + count_vm_event(THP_SPLIT);
> > +
> > page = pmd_page(*pmd);
> > VM_BUG_ON(!page_count(page));
> > get_page(page);
>
> Hey Andi,
>
> Your split counter tracks the split_huge_page_pmd() calls, but misses
> plain split_huge_page() calls. Did you do this on purpose? Could we
> move the counter in to the low-level split function like below?
Agreed, I already noticed and posted this same change in Message-ID:
20110224041851.GF31195
> diff -puN mm/huge_memory.c~move-THP_SPLIT mm/huge_memory.c
> --- linux-2.6.git/mm/huge_memory.c~move-THP_SPLIT 2011-02-24 14:37:32.825288409 -0800
> +++ linux-2.6.git-dave/mm/huge_memory.c 2011-02-24 14:39:01.767939971 -0800
> @@ -1342,6 +1342,8 @@ static void __split_huge_page(struct pag
> BUG_ON(!PageHead(page));
> BUG_ON(PageTail(page));
>
> + count_vm_event(THP_SPLIT);
> +
> mapcount = 0;
> list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
> struct vm_area_struct *vma = avc->vma;
I've a micropreference in having it in split_huge_page succeeding path
after __split_huge_page returns, as the __ function is where the
brainer code is and statcode to me is annoying to read mixed in the
more complex code. Not that it makes any practical difference though.
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