Re: [PATCH 30/35] autonuma: reset autonuma page data when pages are freed

Peter Zijlstra
2012-05-29T16:30:50Z

On Fri, 2012-05-25 at 19:02 +0200, Andrea Arcangeli wrote:
> When pages are freed abort any pending migration. If knuma_migrated
> arrives first it will notice because get_page_unless_zero would fail.

But knuma_migrated can run on a different cpu than this free is
happening, ACCESS_ONCE() won't cure that.

What's that ACCESS_ONCE() good for?

Also, you already have an autonuma_ hook right there, why add more
#ifdeffery ?

> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
> mm/page_alloc.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3d1ee70..1d3163f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -614,6 +614,10 @@ static inline int free_pages_check(struct page *page)
> bad_page(page);
> return 1;
> }
> + autonuma_migrate_page_remove(page);
> +#ifdef CONFIG_AUTONUMA
> + ACCESS_ONCE(page->autonuma_last_nid) = -1;
> +#endif
> if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
> page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
> return 0;