On Wed, Oct 22, 2014 at 01:39:36PM -0700, Andrew Morton wrote: > On Wed, 22 Oct 2014 14:29:28 -0400 Johannes Weiner <[email protected]> wrote: > > @@ -1061,9 +1062,10 @@ void page_add_file_rmap(struct page *page) > > */ > > void page_remove_rmap(struct page *page) > > { > > + struct mem_cgroup *uninitialized_var(memcg); > > bool anon = PageAnon(page); > > - bool locked; > > unsigned long flags; > > + bool locked; > > > > /* > > * The anon case has no mem_cgroup page_stat to update; but may > > @@ -1071,7 +1073,7 @@ void page_remove_rmap(struct page *page) > > * we hold the lock against page_stat move: so avoid it on anon. > > */ > > if (!anon) > > - mem_cgroup_begin_update_page_stat(page, &locked, &flags); > > + memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); > > > > /* page still mapped by someone else? */ > > if (!atomic_add_negative(-1, &page->_mapcount)) > > @@ -1096,8 +1098,7 @@ void page_remove_rmap(struct page *page) > > -hpage_nr_pages(page)); > > } else { > > __dec_zone_page_state(page, NR_FILE_MAPPED); > > - mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED); > > - mem_cgroup_end_update_page_stat(page, &locked, &flags); > > + mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED); > > } > > if (unlikely(PageMlocked(page))) > > clear_page_mlock(page); > > @@ -1110,10 +1111,9 @@ void page_remove_rmap(struct page *page) > > * Leaving it set also helps swapoff to reinstate ptes > > * faster for those pages still in swapcache. > > */ > > - return; > > out: > > if (!anon) > > - mem_cgroup_end_update_page_stat(page, &locked, &flags); > > + mem_cgroup_end_page_stat(memcg, locked, flags); > > } > > The anon and file paths have as much unique code as they do common > code. I wonder if page_remove_rmap() would come out better if split > into two functions? I gave that a quick try and it came out OK-looking.
I agree, that looks better. How about this? --- >From b518d88254b01be8c6c0c4a496d9f311f0c71b4a Mon Sep 17 00:00:00 2001 From: Johannes Weiner <[email protected]> Date: Thu, 23 Oct 2014 09:29:06 -0400 Subject: [patch] mm: rmap: split out page_remove_file_rmap() page_remove_rmap() has too many branches on PageAnon() and is hard to follow. Move the file part into a separate function. Signed-off-by: Johannes Weiner <[email protected]> --- mm/rmap.c | 78 +++++++++++++++++++++++++++++++++++++-------------------------- 1 file changed, 46 insertions(+), 32 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index f574046f77d4..19886fb2f13a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1054,6 +1054,36 @@ void page_add_file_rmap(struct page *page) mem_cgroup_end_page_stat(memcg, locked, flags); } +static void page_remove_file_rmap(struct page *page) +{ + struct mem_cgroup *memcg; + unsigned long flags; + bool locked; + + memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); + + /* page still mapped by someone else? */ + if (!atomic_add_negative(-1, &page->_mapcount)) + goto out; + + /* Hugepages are not counted in NR_FILE_MAPPED for now. */ + if (unlikely(PageHuge(page))) + goto out; + + /* + * We use the irq-unsafe __{inc|mod}_zone_page_stat because + * these counters are not modified in interrupt context, and + * pte lock(a spinlock) is held, which implies preemption disabled. + */ + __dec_zone_page_state(page, NR_FILE_MAPPED); + mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED); + + if (unlikely(PageMlocked(page))) + clear_page_mlock(page); +out: + mem_cgroup_end_page_stat(memcg, locked, flags); +} + /** * page_remove_rmap - take down pte mapping from a page * @page: page to remove mapping from @@ -1062,46 +1092,33 @@ void page_add_file_rmap(struct page *page) */ void page_remove_rmap(struct page *page) { - struct mem_cgroup *uninitialized_var(memcg); - bool anon = PageAnon(page); - unsigned long flags; - bool locked; - - /* - * The anon case has no mem_cgroup page_stat to update; but may - * uncharge_page() below, where the lock ordering can deadlock if - * we hold the lock against page_stat move: so avoid it on anon. - */ - if (!anon) - memcg = mem_cgroup_begin_page_stat(page, &locked, &flags); + if (!PageAnon(page)) { + page_remove_file_rmap(page); + return; + } /* page still mapped by someone else? */ if (!atomic_add_negative(-1, &page->_mapcount)) - goto out; + return; + + /* Hugepages are not counted in NR_ANON_PAGES for now. */ + if (unlikely(PageHuge(page))) + return; /* - * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED - * and not charged by memcg for now. - * * We use the irq-unsafe __{inc|mod}_zone_page_stat because * these counters are not modified in interrupt context, and - * these counters are not modified in interrupt context, and * pte lock(a spinlock) is held, which implies preemption disabled. */ - if (unlikely(PageHuge(page))) - goto out; - if (anon) { - if (PageTransHuge(page)) - __dec_zone_page_state(page, - NR_ANON_TRANSPARENT_HUGEPAGES); - __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, - -hpage_nr_pages(page)); - } else { - __dec_zone_page_state(page, NR_FILE_MAPPED); - mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED); - } + if (PageTransHuge(page)) + __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); + + __mod_zone_page_state(page_zone(page), NR_ANON_PAGES, + -hpage_nr_pages(page)); + if (unlikely(PageMlocked(page))) clear_page_mlock(page); + /* * It would be tidy to reset the PageAnon mapping here, * but that might overwrite a racing page_add_anon_rmap @@ -1111,9 +1128,6 @@ void page_remove_rmap(struct page *page) * Leaving it set also helps swapoff to reinstate ptes * faster for those pages still in swapcache. */ -out: - if (!anon) - mem_cgroup_end_page_stat(memcg, locked, flags); } /* -- 2.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
