linux-kernel - Re: [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation from unspecified node

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Message-ID: <Yd6Xr7K9bKGVgGtI@dhcp22.suse.cz>
Date:   Wed, 12 Jan 2022 09:56:15 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     hannes@...xchg.org, vdavydov.dev@...il.com,
        akpm@...ux-foundation.org, shakeelb@...gle.com, guro@...com,
        vbabka@...e.cz, willy@...radead.org, songmuchun@...edance.com,
        shy828301@...il.com, surenb@...gle.com,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation
 from unspecified node

On Wed 12-01-22 00:46:34, Wei Yang wrote:
> On Tue, Jan 11, 2022 at 09:40:20AM +0100, Michal Hocko wrote:
> >On Tue 11-01-22 01:02:59, Wei Yang wrote:
> >> Instead of use "-1", let's use NUMA_NO_NODE for consistency.
> >> 
> >> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> >
> >I am not really sure this is worth it. After the merge window I plan to
> >post http://lkml.kernel.org/r/20211214100732.26335-1-mhocko@kernel.org.
> 
> Give me some time to understand it :-)

Just for the record, here is what I have put on top of that series:
--- 
>From b7195eba02fe6308a6927450f4630057c05e808e Mon Sep 17 00:00:00 2001
From: Wei Yang <richard.weiyang@...il.com>
Date: Tue, 11 Jan 2022 09:45:25 +0100
Subject: [PATCH] memcg: do not tweak node in alloc_mem_cgroup_per_node_info

alloc_mem_cgroup_per_node_info is allocated for each possible node and
this used to be a problem because not !node_online nodes didn't have
appropriate data structure allocated. This has changed by "mm: handle
uninitialized numa nodes gracefully" so we can drop the special casing
here.

Signed-off-by: Wei Yang <richard.weiyang@...il.com>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 mm/memcontrol.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 781605e92015..ed19a21ee14e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5044,18 +5044,8 @@ struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
 static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
 {
 	struct mem_cgroup_per_node *pn;
-	int tmp = node;
-	/*
-	 * This routine is called against possible nodes.
-	 * But it's BUG to call kmalloc() against offline node.
-	 *
-	 * TODO: this routine can waste much memory for nodes which will
-	 *       never be onlined. It's better to use memory hotplug callback
-	 *       function.
-	 */
-	if (!node_state(node, N_NORMAL_MEMORY))
-		tmp = -1;
-	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
+
+	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, node);
 	if (!pn)
 		return 1;
 
-- 
2.30.2


-- 
Michal Hocko
SUSE Labs