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

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Date:   Fri, 14 Jan 2022 00:29:37 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Wei Yang <richard.weiyang@...il.com>, 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, Jan 12, 2022 at 09:56:15AM +0100, Michal Hocko wrote:
>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:

Ok, I got what you try to resolve. I am ok with the following change except
one point.

>--- 
>>>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.
>-	 */

Do you think this TODO is not related to this change?

>-	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

-- 
Wei Yang
Help you, Help me