[PATCH -mmotm 1/2] memcg move charge of file cache at task migration

[Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>]

This patch adds support for moving charge of file cache. It's enabled by setting
bit 1 of <target cgroup>/memory.move_charge_at_immigrate.

Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
---
 Documentation/cgroups/memory.txt |    6 ++++--
 mm/memcontrol.c                  |   14 +++++++++++---
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 1b5bd04..f53d220 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -461,10 +461,12 @@ charges should be moved.
    0  | A charge of an anonymous page(or swap of it) used by the target task.
       | Those pages and swaps must be used only by the target task. You must
       | enable Swap Extension(see 2.4) to enable move of swap charges.
+ -----+------------------------------------------------------------------------
+   1  | A charge of file cache mmap'ed by the target task. Those pages must be
+      | mmap'ed only by the target task.
 
 Note: Those pages and swaps must be charged to the old cgroup.
-Note: More type of pages(e.g. file cache, shmem,) will be supported by other
-      bits in future.
+Note: More type of pages(e.g. shmem) will be supported by other bits in future.
 
 8.3 TODO
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f6c9d42..66d2704 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -250,6 +250,7 @@ struct mem_cgroup {
  */
 enum move_type {
 	MOVE_CHARGE_TYPE_ANON,	/* private anonymous page and swap of it */
+	MOVE_CHARGE_TYPE_FILE,	/* private file caches */
 	NR_MOVE_TYPE,
 };
 
@@ -4192,6 +4193,8 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
 	int usage_count = 0;
 	bool move_anon = test_bit(MOVE_CHARGE_TYPE_ANON,
 					&mc.to->move_charge_at_immigrate);
+	bool move_file = test_bit(MOVE_CHARGE_TYPE_FILE,
+					&mc.to->move_charge_at_immigrate);
 
 	if (!pte_present(ptent)) {
 		/* TODO: handle swap of shmes/tmpfs */
@@ -4208,10 +4211,15 @@ static int is_target_pte_for_mc(struct vm_area_struct *vma,
 		if (!page || !page_mapped(page))
 			return 0;
 		/*
-		 * TODO: We don't move charges of file(including shmem/tmpfs)
-		 * pages for now.
+		 * TODO: We don't move charges of shmem/tmpfs pages for now.
 		 */
-		if (!move_anon || !PageAnon(page))
+		if (PageAnon(page)) {
+			if (!move_anon)
+				return 0;
+		} else if (page_is_file_cache(page)) {
+			if (!move_file)
+				return 0;
+		} else
 			return 0;
 		if (!get_page_unless_zero(page))
 			return 0;
-- 
1.6.4

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