linux-kernel - Re: + memcg-do-not-tweak-node-in-alloc_mem_cgroup_per_node

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Date:   Tue, 1 Feb 2022 11:02:07 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     linux-kernel@...r.kernel.org
Cc:     mm-commits@...r.kernel.org, tj@...nel.org, rppt@...ux.ibm.com,
        raquini@...hat.com, osalvador@...e.de, npache@...hat.com,
        eric.dumazet@...il.com, dennis@...nel.org, david@...hat.com,
        cl@...ux.com, amakhalov@...are.com, richard.weiyang@...il.com,
        akpm@...ux-foundation.org
Subject: Re: +
 memcg-do-not-tweak-node-in-alloc_mem_cgroup_per_node_info.patch added to -mm
 tree

On Mon 31-01-22 14:19:01, Andrew Morton wrote:
> From: Wei Yang <richard.weiyang@...il.com>
> Subject: 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

Wei has pointed to my typo here. s@not !node_online@...line@

> appropriate data structure allocated.  This has changed by "mm: handle
> uninitialized numa nodes gracefully" so we can drop the special casing
> here.
> 
> Link: https://lkml.kernel.org/r/20220127085305.20890-7-mhocko@kernel.org
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Alexey Makhalov <amakhalov@...are.com>
> Cc: Dennis Zhou <dennis@...nel.org>
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Nico Pache <npache@...hat.com>
> Cc: Wei Yang <richard.weiyang@...il.com>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Rafael Aquini <raquini@...hat.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  mm/memcontrol.c |   14 ++------------
>  1 file changed, 2 insertions(+), 12 deletions(-)
> 
> --- a/mm/memcontrol.c~memcg-do-not-tweak-node-in-alloc_mem_cgroup_per_node_info
> +++ a/mm/memcontrol.c
> @@ -5067,18 +5067,8 @@ struct mem_cgroup *mem_cgroup_from_id(un
>  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;
>  
> _
> 
> Patches currently in -mm which might be from richard.weiyang@...il.com are
> 
> mm-page_alloc-add-same-penalty-is-enough-to-get-round-robin-order.patch
> mm-page_alloc-add-penalty-to-local_node.patch
> memcg-do-not-tweak-node-in-alloc_mem_cgroup_per_node_info.patch

-- 
Michal Hocko
SUSE Labs