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Date:   Sat, 15 Jan 2022 22:10:23 +0000
From:   Wei Yang <richard.weiyang@gmail.com>
To:     Michal Hocko <mhocko@suse.com>
Cc:     Wei Yang <richard.weiyang@gmail.com>, hannes@cmpxchg.org,
        vdavydov.dev@gmail.com, akpm@linux-foundation.org,
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        surenb@google.com, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/4] mm/memcg: use NUMA_NO_NODE to indicate allocation
 from unspecified node
Message-ID: <20220115221023.qndjlehjxdrj5r6b@master>
Reply-To: Wei Yang <richard.weiyang@gmail.com>
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On Fri, Jan 14, 2022 at 09:51:31AM +0100, Michal Hocko wrote:
>On Fri 14-01-22 00:29:37, Wei Yang wrote:
>> 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@gmail.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@gmail.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@gmail.com>
>> >Signed-off-by: Michal Hocko <mhocko@suse.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?
>
>It is not really related but I am not sure how useful it is. Essentially
>any allocation that is per-possible node is in the same situation and if
>we really need to deal with large and sparse possible nodes masks.
>

Sounds reasonable :-)

>If you want me to keep the TODO I will do it though.
>
>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me