On Mon, 2 Mar 2020 19:00:12 +0800 Alex Shi wrote:
>
> As Konstantin Khlebnikov mentioned:
>
> Also I don't like these functions:
> - called lock/unlock but actually also isolates
> - used just once
> - pgdat evaluated twice
>
> Cleanup and fold these functions into commit_charge. It also reduces
> lock time while lrucare && !PageLRU.
>
> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: cgroups@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> mm/memcontrol.c | 57 ++++++++++++++++++++-------------------------------------
> 1 file changed, 20 insertions(+), 37 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d09776cd6e10..875e2aebcde7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2572,41 +2572,11 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
> css_put_many(&memcg->css, nr_pages);
> }
>
> -static void lock_page_lru(struct page *page, int *isolated)
> -{
> - pg_data_t *pgdat = page_pgdat(page);
> -
> - spin_lock_irq(&pgdat->lru_lock);
> - if (PageLRU(page)) {
> - struct lruvec *lruvec;
> -
> - lruvec = mem_cgroup_page_lruvec(page, pgdat);
> - ClearPageLRU(page);
> - del_page_from_lru_list(page, lruvec, page_lru(page));
> - *isolated = 1;
> - } else
> - *isolated = 0;
> -}
> -
> -static void unlock_page_lru(struct page *page, int isolated)
> -{
> - pg_data_t *pgdat = page_pgdat(page);
> -
> - if (isolated) {
> - struct lruvec *lruvec;
> -
> - lruvec = mem_cgroup_page_lruvec(page, pgdat);
> - VM_BUG_ON_PAGE(PageLRU(page), page);
> - SetPageLRU(page);
> - add_page_to_lru_list(page, lruvec, page_lru(page));
> - }
> - spin_unlock_irq(&pgdat->lru_lock);
> -}
> -
> static void commit_charge(struct page *page, struct mem_cgroup *memcg,
> bool lrucare)
> {
> - int isolated;
> + struct lruvec *lruvec = NULL;
> + pg_data_t *pgdat;
>
> VM_BUG_ON_PAGE(page->mem_cgroup, page);
>
> @@ -2614,9 +2584,17 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
> * In some cases, SwapCache and FUSE(splice_buf->radixtree), the page
> * may already be on some other mem_cgroup's LRU. Take care of it.
> */
> - if (lrucare)
> - lock_page_lru(page, &isolated);
> -
> + if (lrucare) {
> + pgdat = page_pgdat(page);
> + spin_lock_irq(&pgdat->lru_lock);
> +
> + if (PageLRU(page)) {
> + lruvec = mem_cgroup_page_lruvec(page, pgdat);
> + ClearPageLRU(page);
> + del_page_from_lru_list(page, lruvec, page_lru(page));
> + } else
> + spin_unlock_irq(&pgdat->lru_lock);
> + }
> /*
> * Nobody should be changing or seriously looking at
> * page->mem_cgroup at this point:
> @@ -2633,8 +2611,13 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
> */
> page->mem_cgroup = memcg;
>
Well it is likely to update memcg for page without lru_lock held even if
more care is required, which is a change added in the current semantic and
worth a line of words in log.
> - if (lrucare)
> - unlock_page_lru(page, isolated);
> + if (lrucare && lruvec) {
> + lruvec = mem_cgroup_page_lruvec(page, pgdat);
> + VM_BUG_ON_PAGE(PageLRU(page), page);
> + SetPageLRU(page);
> + add_page_to_lru_list(page, lruvec, page_lru(page));
> + spin_unlock_irq(&pgdat->lru_lock);
> + }
> }
>
> #ifdef CONFIG_MEMCG_KMEM
> --
> 1.8.3.1
>
>
