[Devel] [PATCH][ just for review] memory controller enhancements [2/5] remember page cache

[KAMEZAWA Hiroyuki]

Add PCGF_PAGECACHE flag to page_cgroup to remember "this page is
charged as page-cache."
This is very useful for implementing precise accounting in memory cgroup.


Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto at valinux.co.jp>

 mm/memcontrol.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Index: devel-2.6.23-rc8-mm2/mm/memcontrol.c
===================================================================
--- devel-2.6.23-rc8-mm2.orig/mm/memcontrol.c
+++ devel-2.6.23-rc8-mm2/mm/memcontrol.c
@@ -83,6 +83,8 @@ struct page_cgroup {
 	struct mem_cgroup *mem_cgroup;
 	atomic_t ref_cnt;		/* Helpful when pages move b/w  */
 					/* mapped and cached states     */
+	int	 flags;
+#define PCGF_PAGECACHE		(0x1)	/* charged as page-cache */
 };
 
 enum {
@@ -305,8 +307,8 @@ unsigned long mem_cgroup_isolate_pages(u
  * 0 if the charge was successful
  * < 0 if the cgroup is over its limit
  */
-int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
-				gfp_t gfp_mask)
+static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
+				gfp_t gfp_mask, int is_cache)
 {
 	struct mem_cgroup *mem;
 	struct page_cgroup *pc;
@@ -406,6 +408,10 @@ noreclaim:
 	atomic_set(&pc->ref_cnt, 1);
 	pc->mem_cgroup = mem;
 	pc->page = page;
+	if (is_cache)
+		pc->flags = PCGF_PAGECACHE;
+	else
+		pc->flags = 0;
 	if (page_cgroup_assign_new_page_cgroup(page, pc)) {
 		/*
 		 * an another charge is added to this page already.
@@ -431,6 +437,12 @@ err:
 	return -ENOMEM;
 }
 
+int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
+			gfp_t gfp_mask)
+{
+	return mem_cgroup_charge_common(page, mm, gfp_mask, 0);
+}
+
 /*
  * See if the cached pages should be charged at all?
  */
@@ -443,7 +455,7 @@ int mem_cgroup_cache_charge(struct page 
 
 	mem = rcu_dereference(mm->mem_cgroup);
 	if (mem->control_type == MEM_CGROUP_TYPE_ALL)
-		return mem_cgroup_charge(page, mm, gfp_mask);
+		return mem_cgroup_charge_common(page, mm, gfp_mask, 1);
 	else
 		return 0;
 }

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