On Mon, Jun 06, 2016 at 03:48:31PM -0400, Johannes Weiner wrote:
> Isolating an existing LRU page and subsequently putting it back on the
> list currently influences the balance between the anon and file LRUs.
> For example, heavy page migration or compaction could influence the
> balance between the LRUs and make one type more attractive when that
> type of page is affected more than the other. That doesn't make sense.
>
> Add a dedicated LRU cache for putback, so that we can tell new LRU
> pages from existing ones at the time of linking them to the lists.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> ---
> include/linux/pagevec.h | 2 +-
> include/linux/swap.h | 1 +
> mm/mlock.c | 2 +-
> mm/swap.c | 34 ++++++++++++++++++++++++++++------
> mm/vmscan.c | 2 +-
> 5 files changed, 32 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
> index b45d391b4540..3f8a2a01131c 100644
> --- a/include/linux/pagevec.h
> +++ b/include/linux/pagevec.h
> @@ -21,7 +21,7 @@ struct pagevec {
> };
>
> void __pagevec_release(struct pagevec *pvec);
> -void __pagevec_lru_add(struct pagevec *pvec);
> +void __pagevec_lru_add(struct pagevec *pvec, bool new);
> unsigned pagevec_lookup_entries(struct pagevec *pvec,
> struct address_space *mapping,
> pgoff_t start, unsigned nr_entries,
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 38fe1e91ba55..178f084365c2 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -296,6 +296,7 @@ extern unsigned long nr_free_pagecache_pages(void);
>
> /* linux/mm/swap.c */
> extern void lru_cache_add(struct page *);
> +extern void lru_cache_putback(struct page *page);
> extern void lru_add_page_tail(struct page *page, struct page *page_tail,
> struct lruvec *lruvec, struct list_head *head);
> extern void activate_page(struct page *);
> diff --git a/mm/mlock.c b/mm/mlock.c
> index 96f001041928..449c291a286d 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -264,7 +264,7 @@ static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
> *__pagevec_lru_add() calls release_pages() so we don't call
> * put_page() explicitly
> */
> - __pagevec_lru_add(pvec);
> + __pagevec_lru_add(pvec, false);
> count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
> }
>
> diff --git a/mm/swap.c b/mm/swap.c
> index c6936507abb5..576c721f210b 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -44,6 +44,7 @@
> int page_cluster;
>
> static DEFINE_PER_CPU(struct pagevec, lru_add_pvec);
> +static DEFINE_PER_CPU(struct pagevec, lru_putback_pvec);
> static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
> static DEFINE_PER_CPU(struct pagevec, lru_deactivate_file_pvecs);
> static DEFINE_PER_CPU(struct pagevec, lru_deactivate_pvecs);
> @@ -405,12 +406,23 @@ void lru_cache_add(struct page *page)
>
> get_page(page);
> if (!pagevec_space(pvec))
> - __pagevec_lru_add(pvec);
> + __pagevec_lru_add(pvec, true);
> pagevec_add(pvec, page);
> put_cpu_var(lru_add_pvec);
> }
> EXPORT_SYMBOL(lru_cache_add);
>
> +void lru_cache_putback(struct page *page)
> +{
> + struct pagevec *pvec = &get_cpu_var(lru_putback_pvec);
> +
> + get_page(page);
> + if (!pagevec_space(pvec))
> + __pagevec_lru_add(pvec, false);
> + pagevec_add(pvec, page);
> + put_cpu_var(lru_putback_pvec);
> +}
> +
> /**
> * add_page_to_unevictable_list - add a page to the unevictable list
> * @page: the page to be added to the unevictable list
> @@ -561,10 +573,15 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec,
> */
> void lru_add_drain_cpu(int cpu)
> {
> - struct pagevec *pvec = &per_cpu(lru_add_pvec, cpu);
> + struct pagevec *pvec;
> +
> + pvec = &per_cpu(lru_add_pvec, cpu);
> + if (pagevec_count(pvec))
> + __pagevec_lru_add(pvec, true);
>
> + pvec = &per_cpu(lru_putback_pvec, cpu);
> if (pagevec_count(pvec))
> - __pagevec_lru_add(pvec);
> + __pagevec_lru_add(pvec, false);
>
> pvec = &per_cpu(lru_rotate_pvecs, cpu);
> if (pagevec_count(pvec)) {
> @@ -819,12 +836,17 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
> int file = page_is_file_cache(page);
> int active = PageActive(page);
> enum lru_list lru = page_lru(page);
> + bool new = (bool)arg;
>
> VM_BUG_ON_PAGE(PageLRU(page), page);
>
> SetPageLRU(page);
> add_page_to_lru_list(page, lruvec, lru);
> - update_page_reclaim_stat(lruvec, file, active, hpage_nr_pages(page));
> +
> + if (new)
> + update_page_reclaim_stat(lruvec, file, active,
> + hpage_nr_pages(page));
> +
> trace_mm_lru_insertion(page, lru);
> }
>
> @@ -832,9 +854,9 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
> * Add the passed pages to the LRU, then drop the caller's refcount
> * on them. Reinitialises the caller's pagevec.
> */
> -void __pagevec_lru_add(struct pagevec *pvec)
> +void __pagevec_lru_add(struct pagevec *pvec, bool new)
> {
> - pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, NULL);
> + pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, (void *)new);
> }
Just trivial:
'new' argument would be not clear in this context what does it mean
so worth to comment it, IMO but no strong opinion.
Other than that,
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
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