linux-kernel - Re: [6/6] mm: memcontrol: account slab stats per lruvec

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Date:   Mon, 5 Jun 2017 13:52:54 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Josef Bacik <josef@...icpanda.com>, Michal Hocko <mhocko@...e.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [6/6] mm: memcontrol: account slab stats per lruvec

On Mon, Jun 05, 2017 at 09:52:03AM -0700, Guenter Roeck wrote:
> On Tue, May 30, 2017 at 02:17:24PM -0400, Johannes Weiner wrote:
> > Josef's redesign of the balancing between slab caches and the page
> > cache requires slab cache statistics at the lruvec level.
> > 
> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> > Acked-by: Vladimir Davydov <vdavydov.dev@...il.com>
> 
> Presumably this is already known, but a remarkable number of crashes
> in next-20170605 bisects to this patch.

Thanks Guenter.

Can you test if the fix below resolves the problem?

---

>From 47007dfcd7873cb93d11466a93b1f41f6a7a434f Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Sun, 4 Jun 2017 07:02:44 -0400
Subject: [PATCH] mm: memcontrol: per-lruvec stats infrastructure fix 2

Even with the previous fix routing !page->mem_cgroup stats to the root
cgroup, we still see crashes in certain configurations as the root is
not initialized for the earliest possible accounting sites in certain
configurations.

Don't track uncharged pages at all, not even in the root. This takes
care of early accounting as well as special pages that aren't tracked.

Because we still need to account at the pgdat level, we can no longer
implement the lruvec_page_state functions on top of the lruvec_state
ones. But that's okay. It was a little silly to look up the nodeinfo
and descend to the lruvec, only to container_of() back to the nodeinfo
where the lruvec_stat structure is sitting.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 include/linux/memcontrol.h | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index bea6f08e9e16..da9360885260 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -585,27 +585,27 @@ static inline void mod_lruvec_state(struct lruvec *lruvec,
 static inline void __mod_lruvec_page_state(struct page *page,
 					   enum node_stat_item idx, int val)
 {
-	struct mem_cgroup *memcg;
-	struct lruvec *lruvec;
-
-	/* Special pages in the VM aren't charged, use root */
-	memcg = page->mem_cgroup ? : root_mem_cgroup;
+	struct mem_cgroup_per_node *pn;
 
-	lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg);
-	__mod_lruvec_state(lruvec, idx, val);
+	__mod_node_page_state(page_pgdat(page), idx, val);
+	if (mem_cgroup_disabled() || !page->mem_cgroup)
+		return;
+	__mod_memcg_state(page->mem_cgroup, idx, val);
+	pn = page->mem_cgroup->nodeinfo[page_to_nid(page)];
+	__this_cpu_add(pn->lruvec_stat->count[idx], val);
 }
 
 static inline void mod_lruvec_page_state(struct page *page,
 					 enum node_stat_item idx, int val)
 {
-	struct mem_cgroup *memcg;
-	struct lruvec *lruvec;
-
-	/* Special pages in the VM aren't charged, use root */
-	memcg = page->mem_cgroup ? : root_mem_cgroup;
+	struct mem_cgroup_per_node *pn;
 
-	lruvec = mem_cgroup_lruvec(page_pgdat(page), memcg);
-	mod_lruvec_state(lruvec, idx, val);
+	mod_node_page_state(page_pgdat(page), idx, val);
+	if (mem_cgroup_disabled() || !page->mem_cgroup)
+		return;
+	mod_memcg_state(page->mem_cgroup, idx, val);
+	pn = page->mem_cgroup->nodeinfo[page_to_nid(page)];
+	this_cpu_add(pn->lruvec_stat->count[idx], val);
 }
 
 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
-- 
2.13.0