On Mon, Dec 28, 2015 at 03:30:26PM -0800, Andrew Morton wrote: > On Thu, 24 Dec 2015 14:51:23 +0300 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > > > During freeze_page(), we remove the page from rmap. It munlocks the page > > if it was mlocked. clear_page_mlock() uses of lru cache, which temporary > > pins page. > > > > Let's drain the lru cache before checking page's count vs. mapcount. > > The change makes mlocked page split on first attempt, if it was not > > pinned by somebody else. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > --- > > mm/huge_memory.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 1a988d9b86ef..4c1c292b7ddd 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -3417,6 +3417,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) > > freeze_page(anon_vma, head); > > VM_BUG_ON_PAGE(compound_mapcount(head), head); > > > > + /* Make sure the page is not on per-CPU pagevec as it takes pin */ > > + lru_add_drain(); > > + > > /* Prevent deferred_split_scan() touching ->_count */ > > spin_lock(&split_queue_lock); > > count = page_count(head); > > Fair enough. > > mlocked pages are rare and lru_add_drain() isn't free. We could easily > and cheaply make page_remove_rmap() return "bool was_mlocked" (or, > better, "bool might_be_in_lru_cache") to skip this overhead. Propagating it back is painful. What about this instead: diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ecb4ed1a821a..edfa53eda9ca 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3385,6 +3385,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) struct page *head = compound_head(page); struct anon_vma *anon_vma; int count, mapcount, ret; + bool mlocked; VM_BUG_ON_PAGE(is_huge_zero_page(page), page); VM_BUG_ON_PAGE(!PageAnon(page), page); @@ -3415,11 +3416,13 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) goto out_unlock; } + mlocked = PageMlocked(page); freeze_page(anon_vma, head); VM_BUG_ON_PAGE(compound_mapcount(head), head); /* Make sure the page is not on per-CPU pagevec as it takes pin */ - lru_add_drain(); + if (mlocked) + lru_add_drain(); /* Prevent deferred_split_scan() touching ->_count */ spin_lock(&split_queue_lock); -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>