Commit e6e88712 authored Oct 13, 2020 by Matthew Wilcox (Oracle) Committed by Linus Torvalds Oct 13, 2020

mm: optimise madvise WILLNEED

Instead of calling find_get_entry() for every page index, use an XArray
iterator to skip over NULL entries, and avoid calling get_page(),
because we only want the swap entries.

[willy@infradead.org: fix LTP soft lockups]
  Link: https://lkml.kernel.org/r/20200914165032.GS6583@casper.infradead.org



Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Qian Cai <cai@redhat.com>
Link: https://lkml.kernel.org/r/20200910183318.20139-4-willy@infradead.org


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f5df8635

mm/madvise.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -224,25 +224,28 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
		unsigned long start, unsigned long end,
		struct address_space *mapping)
		{
		pgoff_t index;
		XA_STATE(xas, &mapping->i_pages, linear_page_index(vma, start));
		pgoff_t end_index = end / PAGE_SIZE;
		struct page *page;
		swp_entry_t swap;

		for (; start < end; start += PAGE_SIZE) {
		index = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
		rcu_read_lock();
		xas_for_each(&xas, page, end_index) {
		swp_entry_t swap;

		page = find_get_entry(mapping, index);
		if (!xa_is_value(page)) {
		if (page)
		put_page(page);
		if (!xa_is_value(page))
		continue;
		}
		xas_pause(&xas);
		rcu_read_unlock();

		swap = radix_to_swp_entry(page);
		page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
		NULL, 0, false);
		if (page)
		put_page(page);

		rcu_read_lock();
		}
		rcu_read_unlock();

		lru_add_drain(); /* Push any new pages onto the LRU now */
		}

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