Re: [v5][PATCH 5/6] mm: vmscan: batch shrink_page_list() locking operations

[Hillf Danton]

On Tue, Jun 4, 2013 at 4:02 AM, Dave Hansen <dave@xxxxxxxx> wrote:
> +/*
> + * pages come in here (via remove_list) locked and leave unlocked
> + * (on either ret_pages or free_pages)
> + *
> + * We do this batching so that we free batches of pages with a
> + * single mapping->tree_lock acquisition/release.  This optimization
> + * only makes sense when the pages on remove_list all share a
> + * page_mapping().  If this is violated you will BUG_ON().
> + */
> +static int __remove_mapping_batch(struct list_head *remove_list,
> +                                 struct list_head *ret_pages,
> +                                 struct list_head *free_pages)
> +{
> +       int nr_reclaimed = 0;
> +       struct address_space *mapping;
> +       struct page *page;
> +       LIST_HEAD(need_free_mapping);
> +
> +       if (list_empty(remove_list))
> +               return 0;
> +
> +       mapping = page_mapping(lru_to_page(remove_list));
> +       spin_lock_irq(&mapping->tree_lock);
> +       while (!list_empty(remove_list)) {
> +               page = lru_to_page(remove_list);
> +               BUG_ON(!PageLocked(page));
> +               BUG_ON(page_mapping(page) != mapping);
> +               list_del(&page->lru);
> +
> +               if (!__remove_mapping(mapping, page)) {
> +                       unlock_page(page);
> +                       list_add(&page->lru, ret_pages);
> +                       continue;
> +               }
> +               list_add(&page->lru, &need_free_mapping);
> +       }
> +       spin_unlock_irq(&mapping->tree_lock);
> +
While reclaiming pages, can we open ears upon IRQ controller,
if the page list length is over 10, or even 20?
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