[PATCH] mm/memcontrol: avoid unnecessary PageTransHuge() when counting compound page

[Yafang Shao <laoar.shao@gmail.com>]

If CONFIG_TRANSPARENT_HUGEPAGE is not set, hpage_nr_pages() is always 1;
if CONFIG_TRANSPARENT_HUGEPAGE is set, hpage_nr_pages() will
call PageTransHuge() to judge whether the page is compound page or not.
So we can use the result of hpage_nr_pages() to avoid uneccessary
PageTransHuge().

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 mm/memcontrol.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2535e54..65c6f7c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6306,7 +6306,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 {
 	struct mem_cgroup *memcg;
 	unsigned int nr_pages;
-	bool compound;
 	unsigned long flags;
 
 	VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
@@ -6328,8 +6327,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 		return;
 
 	/* Force-charge the new page. The old one will be freed soon */
-	compound = PageTransHuge(newpage);
-	nr_pages = compound ? hpage_nr_pages(newpage) : 1;
+	nr_pages = hpage_nr_pages(newpage);
 
 	page_counter_charge(&memcg->memory, nr_pages);
 	if (do_memsw_account())
@@ -6339,7 +6337,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 	commit_charge(newpage, memcg, false);
 
 	local_irq_save(flags);
-	mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages);
+	mem_cgroup_charge_statistics(memcg, newpage, nr_pages > 1, nr_pages);
 	memcg_check_events(memcg, newpage);
 	local_irq_restore(flags);
 }
@@ -6533,6 +6531,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	struct mem_cgroup *memcg, *swap_memcg;
 	unsigned int nr_entries;
 	unsigned short oldid;
+	bool compound;
 
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 	VM_BUG_ON_PAGE(page_count(page), page);
@@ -6553,8 +6552,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	 */
 	swap_memcg = mem_cgroup_id_get_online(memcg);
 	nr_entries = hpage_nr_pages(page);
+	compound = nr_entries > 1;
 	/* Get references for the tail pages, too */
-	if (nr_entries > 1)
+	if (compound)
 		mem_cgroup_id_get_many(swap_memcg, nr_entries - 1);
 	oldid = swap_cgroup_record(entry, mem_cgroup_id(swap_memcg),
 				   nr_entries);
@@ -6579,8 +6579,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
 	 * only synchronisation we have for updating the per-CPU variables.
 	 */
 	VM_BUG_ON(!irqs_disabled());
-	mem_cgroup_charge_statistics(memcg, page, PageTransHuge(page),
-				     -nr_entries);
+	mem_cgroup_charge_statistics(memcg, page, compound, -nr_entries);
 	memcg_check_events(memcg, page);
 
 	if (!mem_cgroup_is_root(memcg))
-- 
1.8.3.1