linux-kernel - Re: [PATCH v2 12/46] mm/memcg: Use the node id in mem_cgroup_update

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Date:   Thu, 24 Jun 2021 17:19:53 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     akpm@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v2 12/46] mm/memcg: Use the node id in
 mem_cgroup_update_tree()

On Wed, Jun 23, 2021 at 10:12:40AM +0200, Christoph Hellwig wrote:
> On Tue, Jun 22, 2021 at 01:15:17PM +0100, Matthew Wilcox (Oracle) wrote:
> >  static struct mem_cgroup_per_node *
> > -mem_cgroup_page_nodeinfo(struct mem_cgroup *memcg, struct page *page)
> > +mem_cgroup_nodeinfo(struct mem_cgroup *memcg, int nid)
> >  {
> > -	int nid = page_to_nid(page);
> > -
> >  	return memcg->nodeinfo[nid];
> >  }
> 
> I'd just kill this function entirely and open code it into the only
> caller

Done.

> > -	mctz = soft_limit_tree_from_page(page);
> > +	mctz = soft_limit_tree_node(nid);
> 
> And while were at it, soft_limit_tree_node seems like a completely
> pointless helper that does nothing but obsfucating the code.  While
> you touch this area it might be worth to spin another patch to just
> remove it as well.

I'm scared that if I touch this file too much, people will start to
think I know something about memcgs.  Happy to add it on; cc'ing
maintainers.