On Fri, 15 Apr 2011 10:38:23 -0700
Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote:
>
> Now that we have the mm in the constructor and destructor, it's
> simple to to bump a counter. Add the counter to the mm and use
> the existing MM_* counter infrastructure.
>
> Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
> ---
>
> linux-2.6.git-dave/include/linux/mm.h | 2 ++
> linux-2.6.git-dave/include/linux/mm_types.h | 1 +
> 2 files changed, 3 insertions(+)
>
> diff -puN include/linux/mm.h~track-pagetable-pages include/linux/mm.h
> --- linux-2.6.git/include/linux/mm.h~track-pagetable-pages 2011-04-15 10:37:10.768832396 -0700
> +++ linux-2.6.git-dave/include/linux/mm.h 2011-04-15 10:37:10.780832393 -0700
> @@ -1245,12 +1245,14 @@ static inline pmd_t *pmd_alloc(struct mm
> static inline void pgtable_page_ctor(struct mm_struct *mm, struct page *page)
> {
> pte_lock_init(page);
> + inc_mm_counter(mm, MM_PTEPAGES);
> inc_zone_page_state(page, NR_PAGETABLE);
> }
>
> static inline void pgtable_page_dtor(struct mm_struct *mm, struct page *page)
> {
> pte_lock_deinit(page);
> + dec_mm_counter(mm, MM_PTEPAGES);
> dec_zone_page_state(page, NR_PAGETABLE);
> }
I'm probably missing something really obvious but...
Is this safe in the non-USE_SPLIT_PTLOCKS case? If we're not using
split-ptlocks then inc/dec_mm_counter() are only safe when done under
mm->page_table_lock, right? But it looks to me like we can end up doing,
__pte_alloc()
pte_alloc_one()
pgtable_page_ctor()
before acquiring mm->page_table_lock in __pte_alloc().
--
Matt Fleming, Intel Open Source Technology Center
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