Hi,
On Tue, Jul 18, 2017 at 07:00:23PM +0300, Konstantin Khlebnikov wrote:
> Pages are added into lru lists via per-cpu page vectors in order
> to combine these insertions and reduce lru lock contention.
>
> These pending pages cannot be isolated and moved into another lru.
> This breaks in some cases page activation and makes mlock-munlock
> much more complicated.
>
> Also this breaks newly added swapless MADV_FREE: if it cannot move
> anon page into file lru then page could never be freed lazily.
Yes, it's really unforunate.
>
> This patch rearranges lru list handling to allow lru isolation for
> such pages. It set PageLRU earlier and initialize page->lru to mark
> pages still pending for lru insert.
At a first glance, it seems to work but it's rather hacky to me.
Could you make mark_page_lazyfree be aware of it?
IOW, mark_page_lazyfree can clear PG_active|referenced|swapbacked under
lru_lock if it was not in the LRU. With it, pagevec handler for LRU
can move pages into proper list when drain happens.
>
> Signed-off-by: Konstantin Khlebnikov <khlebni...@yandex-team.ru>
> ---
> include/linux/mm_inline.h | 10 ++++++++--
> mm/swap.c | 26 ++++++++++++++++++++++++--
> 2 files changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index e030a68ead7e..6618c588ee40 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -60,8 +60,14 @@ static __always_inline void
> add_page_to_lru_list_tail(struct page *page,
> static __always_inline void del_page_from_lru_list(struct page *page,
> struct lruvec *lruvec, enum lru_list lru)
> {
> - list_del(&page->lru);
> - update_lru_size(lruvec, lru, page_zonenum(page), -hpage_nr_pages(page));
> + /*
> + * Empty list head means page is not drained to lru list yet.
> + */
> + if (likely(!list_empty(&page->lru))) {
> + list_del(&page->lru);
> + update_lru_size(lruvec, lru, page_zonenum(page),
> + -hpage_nr_pages(page));
> + }
> }
>
> /**
> diff --git a/mm/swap.c b/mm/swap.c
> index 23fc6e049cda..ba4c98074a09 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -400,13 +400,35 @@ void mark_page_accessed(struct page *page)
> }
> EXPORT_SYMBOL(mark_page_accessed);
>
> +static void __pagevec_lru_add_drain_fn(struct page *page, struct lruvec
> *lruvec,
> + void *arg)
> +{
> + /* Check for isolated or already added pages */
> + if (likely(PageLRU(page) && list_empty(&page->lru))) {
> + int file = page_is_file_cache(page);
> + int active = PageActive(page);
> + enum lru_list lru = page_lru(page);
> +
> + add_page_to_lru_list(page, lruvec, lru);
> + update_page_reclaim_stat(lruvec, file, active);
> + trace_mm_lru_insertion(page, lru);
> + }
> +}
> +
> static void __lru_cache_add(struct page *page)
> {
> struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
>
> + /*
> + * Set PageLRU right here and initialize list head to
> + * allow page isolation while it on the way to the LRU list.
> + */
> + VM_BUG_ON_PAGE(PageLRU(page), page);
> + INIT_LIST_HEAD(&page->lru);
> get_page(page);
> + SetPageLRU(page);
> if (!pagevec_add(pvec, page) || PageCompound(page))
> - __pagevec_lru_add(pvec);
> + pagevec_lru_move_fn(pvec, __pagevec_lru_add_drain_fn, NULL);
> put_cpu_var(lru_add_pvec);
> }
>
> @@ -611,7 +633,7 @@ void lru_add_drain_cpu(int cpu)
> struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
>
> if (pagevec_count(pvec))
> - __pagevec_lru_add(pvec);
> + pagevec_lru_move_fn(pvec, __pagevec_lru_add_drain_fn, NULL);
>
> pvec = &per_cpu(lru_rotate_pvecs, cpu);
> if (pagevec_count(pvec)) {
>
> --
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