From 802a3a92ad7ac0b9be9df229dee530a1f0a8039b Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Wed, 3 May 2017 14:52:32 -0700 Subject: mm: reclaim MADV_FREE pages When memory pressure is high, we free MADV_FREE pages. If the pages are not dirty in pte, the pages could be freed immediately. Otherwise we can't reclaim them. We put the pages back to anonumous LRU list (by setting SwapBacked flag) and the pages will be reclaimed in normal swapout way. We use normal page reclaim policy. Since MADV_FREE pages are put into inactive file list, such pages and inactive file pages are reclaimed according to their age. This is expected, because we don't want to reclaim too many MADV_FREE pages before used once pages. Based on Minchan's original patch [minchan@kernel.org: clean up lazyfree page handling] Link: http://lkml.kernel.org/r/20170303025237.GB3503@bbox Link: http://lkml.kernel.org/r/14b8eb1d3f6bf6cc492833f183ac8c304e560484.1487965799.git.shli@fb.com Signed-off-by: Shaohua Li Signed-off-by: Minchan Kim Acked-by: Minchan Kim Acked-by: Michal Hocko Acked-by: Johannes Weiner Acked-by: Hillf Danton Cc: Hugh Dickins Cc: Rik van Riel Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 46 ++++++++++++++++++++-------------------------- 1 file changed, 20 insertions(+), 26 deletions(-) (limited to 'mm/rmap.c') diff --git a/mm/rmap.c b/mm/rmap.c index b4084d09dbe8..519b7eb723d1 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1288,11 +1288,6 @@ void page_remove_rmap(struct page *page, bool compound) */ } -struct rmap_private { - enum ttu_flags flags; - int lazyfreed; -}; - /* * @arg: enum ttu_flags will be passed to this argument */ @@ -1308,8 +1303,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, pte_t pteval; struct page *subpage; int ret = SWAP_AGAIN; - struct rmap_private *rp = arg; - enum ttu_flags flags = rp->flags; + enum ttu_flags flags = (enum ttu_flags)arg; /* munlock has nothing to gain from examining un-locked vmas */ if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) @@ -1427,11 +1421,21 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page), page); - if (!PageDirty(page)) { - /* It's a freeable page by MADV_FREE */ - dec_mm_counter(mm, MM_ANONPAGES); - rp->lazyfreed++; - goto discard; + /* MADV_FREE page check */ + if (!PageSwapBacked(page)) { + if (!PageDirty(page)) { + dec_mm_counter(mm, MM_ANONPAGES); + goto discard; + } + + /* + * If the page was redirtied, it cannot be + * discarded. Remap the page to page table. + */ + set_pte_at(mm, address, pvmw.pte, pteval); + ret = SWAP_DIRTY; + page_vma_mapped_walk_done(&pvmw); + break; } if (swap_duplicate(entry) < 0) { @@ -1499,18 +1503,15 @@ static int page_mapcount_is_zero(struct page *page) * SWAP_AGAIN - we missed a mapping, try again later * SWAP_FAIL - the page is unswappable * SWAP_MLOCK - page is mlocked. + * SWAP_DIRTY - page is dirty MADV_FREE page */ int try_to_unmap(struct page *page, enum ttu_flags flags) { int ret; - struct rmap_private rp = { - .flags = flags, - .lazyfreed = 0, - }; struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, - .arg = &rp, + .arg = (void *)flags, .done = page_mapcount_is_zero, .anon_lock = page_lock_anon_vma_read, }; @@ -1531,11 +1532,8 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) else ret = rmap_walk(page, &rwc); - if (ret != SWAP_MLOCK && !page_mapcount(page)) { + if (ret != SWAP_MLOCK && !page_mapcount(page)) ret = SWAP_SUCCESS; - if (rp.lazyfreed && !PageDirty(page)) - ret = SWAP_LZFREE; - } return ret; } @@ -1562,14 +1560,10 @@ static int page_not_mapped(struct page *page) int try_to_munlock(struct page *page) { int ret; - struct rmap_private rp = { - .flags = TTU_MUNLOCK, - .lazyfreed = 0, - }; struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, - .arg = &rp, + .arg = (void *)TTU_MUNLOCK, .done = page_not_mapped, .anon_lock = page_lock_anon_vma_read, -- cgit v1.2.3-59-g8ed1b