Re: [RFC PATCH -tip 0/2 v3] pagecache tracepoints proposal

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Feb 18, 2010 at 05:58:50PM +0800, Balbir Singh wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-02-18 14:34:29]:
> > Can we dump page's cgroup ? If so, I'm happy.
> > Maybe
> > ==
> >   struct page_cgroup *pc = lookup_page_cgroup(page);
> >   struct mem_cgroup *mem = pc->mem_cgroup;
> >   shodt mem_cgroup_id = mem->css.css_id;
> > 
> >   And statistics can be counted per css_id.
> >
> 
> Good idea, all of this needs to happen with a check to see if memcg is
> enabled/disabled at boot as well. pc can be NULL if
> CONFIG_CGROUP_MEM_RES_CTLR is not enabled.

Not sure if this is the one in your mind, but I defined a function in
memcontrol.c for the trace code. Compile tested.

It'll be used like this:

        TP_fast_assign(
                        __entry->memcg          = page_memcg_id(page);
                      )

        TP_printk("index=%lu len=%lu flags=%lx count=%u mapcount=%u memcg=%d",

Thanks,
Fengguang

---
memcg: introduce page_memcg_id()

This will be used to dump the memcg id associated with a pagecache page.

CC: Balbir Singh <balbir@linux.vnet.ibm.com>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/memcontrol.h |    6 ++++++
 mm/memcontrol.c            |   16 ++++++++++++++++
 2 files changed, 22 insertions(+)

--- linux-mm.orig/include/linux/memcontrol.h	2010-02-23 21:49:39.000000000 +0800
+++ linux-mm/include/linux/memcontrol.h	2010-02-23 21:50:14.000000000 +0800
@@ -69,6 +69,7 @@ extern void mem_cgroup_out_of_memory(str
 int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem);
 
 extern struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page);
+extern unsigned short page_memcg_id(struct page *page);
 extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 
 static inline
@@ -142,6 +143,11 @@ static inline int mem_cgroup_try_charge_
 	return 0;
 }
 
+static inline unsigned short page_memcg_id(struct page *page)
+{
+	return 0;
+}
+
 static inline void mem_cgroup_commit_charge_swapin(struct page *page,
 					  struct mem_cgroup *ptr)
 {
--- linux-mm.orig/mm/memcontrol.c	2010-02-23 21:48:23.000000000 +0800
+++ linux-mm/mm/memcontrol.c	2010-02-23 21:49:33.000000000 +0800
@@ -324,6 +324,22 @@ static struct mem_cgroup *try_get_mem_cg
 	return mem;
 }
 
+unsigned short page_memcg_id(struct page *page)
+{
+	struct mem_cgroup *mem;
+	struct cgroup_subsys_state *css;
+	unsigned short id = 0;
+
+	mem = try_get_mem_cgroup_from_page(page);
+	if (mem) {
+		css = mem_cgroup_css(mem);
+		id = css_id(css);
+		css_put(css);
+	}
+
+	return id;
+}
+
 /*
  * Call callback function against all cgroup under hierarchy tree.
  */