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SubjectRe: [PATCH v19 07/20] mm/vmscan: remove unnecessary lruvec adding
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This patch has some conflict on akpm. But since Yu Zhao ask for
revert his patch 'mm: use add_page_to_lru_list()/page_lru()/page_off_lru()'
we should not needs for rebase on it.

Thanks
Alex

在 2020/9/24 上午11:28, Alex Shi 写道:
> We don't have to add a freeable page into lru and then remove from it.
> This change saves a couple of actions and makes the moving more clear.
>
> The SetPageLRU needs to be kept before put_page_testzero for list
> integrity, otherwise:
>
> #0 move_pages_to_lru #1 release_pages
> if !put_page_testzero
> if (put_page_testzero())
> !PageLRU //skip lru_lock
> SetPageLRU()
> list_add(&page->lru,)
> list_add(&page->lru,)
>
> [akpm@linux-foundation.org: coding style fixes]
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Acked-by: Hugh Dickins <hughd@google.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
> mm/vmscan.c | 38 +++++++++++++++++++++++++-------------
> 1 file changed, 25 insertions(+), 13 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 466fc3144fff..32102e5d354d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1850,26 +1850,30 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> while (!list_empty(list)) {
> page = lru_to_page(list);
> VM_BUG_ON_PAGE(PageLRU(page), page);
> + list_del(&page->lru);
> if (unlikely(!page_evictable(page))) {
> - list_del(&page->lru);
> spin_unlock_irq(&pgdat->lru_lock);
> putback_lru_page(page);
> spin_lock_irq(&pgdat->lru_lock);
> continue;
> }
> - lruvec = mem_cgroup_page_lruvec(page, pgdat);
>
> + /*
> + * The SetPageLRU needs to be kept here for list integrity.
> + * Otherwise:
> + * #0 move_pages_to_lru #1 release_pages
> + * if !put_page_testzero
> + * if (put_page_testzero())
> + * !PageLRU //skip lru_lock
> + * SetPageLRU()
> + * list_add(&page->lru,)
> + * list_add(&page->lru,)
> + */
> SetPageLRU(page);
> - lru = page_lru(page);
>
> - nr_pages = thp_nr_pages(page);
> - update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
> - list_move(&page->lru, &lruvec->lists[lru]);
> -
> - if (put_page_testzero(page)) {
> + if (unlikely(put_page_testzero(page))) {
> __ClearPageLRU(page);
> __ClearPageActive(page);
> - del_page_from_lru_list(page, lruvec, lru);
>
> if (unlikely(PageCompound(page))) {
> spin_unlock_irq(&pgdat->lru_lock);
> @@ -1877,11 +1881,19 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> spin_lock_irq(&pgdat->lru_lock);
> } else
> list_add(&page->lru, &pages_to_free);
> - } else {
> - nr_moved += nr_pages;
> - if (PageActive(page))
> - workingset_age_nonresident(lruvec, nr_pages);
> +
> + continue;
> }
> +
> + lruvec = mem_cgroup_page_lruvec(page, pgdat);
> + lru = page_lru(page);
> + nr_pages = thp_nr_pages(page);
> +
> + update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
> + list_add(&page->lru, &lruvec->lists[lru]);
> + nr_moved += nr_pages;
> + if (PageActive(page))
> + workingset_age_nonresident(lruvec, nr_pages);
> }
>
> /*
>

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