Re: [PATCH 2/2] mm/memcontrol.c: introduce helper mem_cgroup_zoneinfo_zone()

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, May 02, 2014 at 03:05:16PM -0700, Andrew Morton wrote:
> On Thu, 1 May 2014 08:54:50 -0400 Johannes Weiner <hannes@cmpxchg.org> wrote:
> 
> > On Mon, Apr 28, 2014 at 05:04:26PM +0200, Michal Hocko wrote:
> > > On Tue 22-04-14 11:59:23, Michal Hocko wrote:
> > > > On Sat 19-04-14 07:01:43, Jianyu Zhan wrote:
> > > > > introduce helper mem_cgroup_zoneinfo_zone(). This will make
> > > > > mem_cgroup_iter() code more compact.
> > > > 
> > > > I dunno. Helpers are usually nice but this one adds more code then it
> > > > removes. It also doesn't help the generated code.
> > > > 
> > > > So I don't see any reason to merge it.
> > > 
> > > So should we drop it from mmotm?
> > 
> > Yes, please.
> > 
> > > > > Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
> > > > > ---
> > > > >  mm/memcontrol.c | 15 +++++++++++----
> > > > >  1 file changed, 11 insertions(+), 4 deletions(-)
> > 
> > This helper adds no value, but more code and indirection.
> > 
> > Cc'd Andrew - this is about
> > mm-memcontrolc-introduce-helper-mem_cgroup_zoneinfo_zone.patch
> > mm-memcontrolc-introduce-helper-mem_cgroup_zoneinfo_zone-checkpatch-fixes.patch
> 
> The patch seemed rather nice to me.  mem_cgroup_zoneinfo_zone()
> encapsulates a particular concept and gives it a name.  That's better
> than splattering the logic into callsites.

Yeah, that helper is actually a good idea, for me it was just drowned
out by the diffstat, the naming, and that the zoneinfo lookup overall
was still left in bad shape.  Thanks for prodding ;-) How about this?

---
From: Jianyu Zhan <nasa4836@gmail.com>
Subject: [patch] mm: memcontrol: clean up memcg zoneinfo lookup

Memcg zoneinfo lookup sites have either the page, the zone, or the
node id and zone index, but sites that only have the zone have to look
up the node id and zone index themselves, whereas sites that already
have those two integers use a function for a simple pointer chase.

Provide mem_cgroup_zone_zoneinfo() that takes a zone pointer and let
sites that already have node id and zone index - all for each node,
for each zone iterators - use &memcg->nodeinfo[nid]->zoneinfo[zid].

Rename page_cgroup_zoneinfo() to mem_cgroup_page_zoneinfo() to match.

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c | 89 +++++++++++++++++++++++++--------------------------------
 1 file changed, 39 insertions(+), 50 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 29501f040568..83cbd5a0e62f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -677,9 +677,11 @@ static void disarm_static_keys(struct mem_cgroup *memcg)
 static void drain_all_stock_async(struct mem_cgroup *memcg);
 
 static struct mem_cgroup_per_zone *
-mem_cgroup_zoneinfo(struct mem_cgroup *memcg, int nid, int zid)
+mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
 {
-	VM_BUG_ON((unsigned)nid >= nr_node_ids);
+	int nid = zone_to_nid(zone);
+	int zid = zone_idx(zone);
+
 	return &memcg->nodeinfo[nid]->zoneinfo[zid];
 }
 
@@ -689,12 +691,12 @@ struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *memcg)
 }
 
 static struct mem_cgroup_per_zone *
-page_cgroup_zoneinfo(struct mem_cgroup *memcg, struct page *page)
+mem_cgroup_page_zoneinfo(struct mem_cgroup *memcg, struct page *page)
 {
 	int nid = page_to_nid(page);
 	int zid = page_zonenum(page);
 
-	return mem_cgroup_zoneinfo(memcg, nid, zid);
+	return &memcg->nodeinfo[nid]->zoneinfo[zid];
 }
 
 static struct mem_cgroup_tree_per_zone *
@@ -773,16 +775,14 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 	unsigned long long excess;
 	struct mem_cgroup_per_zone *mz;
 	struct mem_cgroup_tree_per_zone *mctz;
-	int nid = page_to_nid(page);
-	int zid = page_zonenum(page);
-	mctz = soft_limit_tree_from_page(page);
 
+	mctz = soft_limit_tree_from_page(page);
 	/*
 	 * Necessary to update all ancestors when hierarchy is used.
 	 * because their event counter is not touched.
 	 */
 	for (; memcg; memcg = parent_mem_cgroup(memcg)) {
-		mz = mem_cgroup_zoneinfo(memcg, nid, zid);
+		mz = mem_cgroup_page_zoneinfo(memcg, page);
 		excess = res_counter_soft_limit_excess(&memcg->res);
 		/*
 		 * We have to update the tree if mz is on RB-tree or
@@ -805,14 +805,14 @@ static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
 
 static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
 {
-	int node, zone;
-	struct mem_cgroup_per_zone *mz;
 	struct mem_cgroup_tree_per_zone *mctz;
+	struct mem_cgroup_per_zone *mz;
+	int nid, zid;
 
-	for_each_node(node) {
-		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
-			mz = mem_cgroup_zoneinfo(memcg, node, zone);
-			mctz = soft_limit_tree_node_zone(node, zone);
+	for_each_node(nid) {
+		for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+			mz = &memcg->nodeinfo[nid]->zoneinfo[zid];
+			mctz = soft_limit_tree_node_zone(nid, zid);
 			mem_cgroup_remove_exceeded(memcg, mz, mctz);
 		}
 	}
@@ -947,8 +947,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
 	__this_cpu_add(memcg->stat->nr_page_events, nr_pages);
 }
 
-unsigned long
-mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
+unsigned long mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
 {
 	struct mem_cgroup_per_zone *mz;
 
@@ -956,46 +955,38 @@ mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
 	return mz->lru_size[lru];
 }
 
-static unsigned long
-mem_cgroup_zone_nr_lru_pages(struct mem_cgroup *memcg, int nid, int zid,
-			unsigned int lru_mask)
-{
-	struct mem_cgroup_per_zone *mz;
-	enum lru_list lru;
-	unsigned long ret = 0;
-
-	mz = mem_cgroup_zoneinfo(memcg, nid, zid);
-
-	for_each_lru(lru) {
-		if (BIT(lru) & lru_mask)
-			ret += mz->lru_size[lru];
-	}
-	return ret;
-}
-
-static unsigned long
-mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
-			int nid, unsigned int lru_mask)
+static unsigned long mem_cgroup_node_nr_lru_pages(struct mem_cgroup *memcg,
+						  int nid,
+						  unsigned int lru_mask)
 {
-	u64 total = 0;
+	unsigned long nr = 0;
 	int zid;
 
-	for (zid = 0; zid < MAX_NR_ZONES; zid++)
-		total += mem_cgroup_zone_nr_lru_pages(memcg,
-						nid, zid, lru_mask);
+	VM_BUG_ON((unsigned)nid >= nr_node_ids);
+
+	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+		struct mem_cgroup_per_zone *mz;
+		enum lru_list lru;
 
-	return total;
+		for_each_lru(lru) {
+			if (!(BIT(lru) & lru_mask))
+				continue;
+			mz = &memcg->nodeinfo[nid]->zoneinfo[zid];
+			nr += mz->lru_size[lru];
+		}
+	}
+	return nr;
 }
 
 static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
 			unsigned int lru_mask)
 {
+	unsigned long nr = 0;
 	int nid;
-	u64 total = 0;
 
 	for_each_node_state(nid, N_MEMORY)
-		total += mem_cgroup_node_nr_lru_pages(memcg, nid, lru_mask);
-	return total;
+		nr += mem_cgroup_node_nr_lru_pages(memcg, nid, lru_mask);
+	return nr;
 }
 
 static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
@@ -1234,11 +1225,9 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
 		int uninitialized_var(seq);
 
 		if (reclaim) {
-			int nid = zone_to_nid(reclaim->zone);
-			int zid = zone_idx(reclaim->zone);
 			struct mem_cgroup_per_zone *mz;
 
-			mz = mem_cgroup_zoneinfo(root, nid, zid);
+			mz = mem_cgroup_zone_zoneinfo(root, reclaim->zone);
 			iter = &mz->reclaim_iter[reclaim->priority];
 			if (prev && reclaim->generation != iter->generation) {
 				iter->last_visited = NULL;
@@ -1345,7 +1334,7 @@ struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
 		goto out;
 	}
 
-	mz = mem_cgroup_zoneinfo(memcg, zone_to_nid(zone), zone_idx(zone));
+	mz = mem_cgroup_zone_zoneinfo(memcg, zone);
 	lruvec = &mz->lruvec;
 out:
 	/*
@@ -1404,7 +1393,7 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct zone *zone)
 	if (!PageLRU(page) && !PageCgroupUsed(pc) && memcg != root_mem_cgroup)
 		pc->mem_cgroup = memcg = root_mem_cgroup;
 
-	mz = page_cgroup_zoneinfo(memcg, page);
+	mz = mem_cgroup_page_zoneinfo(memcg, page);
 	lruvec = &mz->lruvec;
 out:
 	/*
@@ -5412,7 +5401,7 @@ static int memcg_stat_show(struct seq_file *m, void *v)
 
 		for_each_online_node(nid)
 			for (zid = 0; zid < MAX_NR_ZONES; zid++) {
-				mz = mem_cgroup_zoneinfo(memcg, nid, zid);
+				mz = &memcg->nodeinfo[nid]->zoneinfo[zid];
 				rstat = &mz->lruvec.reclaim_stat;
 
 				recent_rotated[0] += rstat->recent_rotated[0];
-- 
1.9.2


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