linux-kernel - Re: [PATCH] mm: memcontrol: fix kernel stack account

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Message-ID: <YD6iJxEDzLInH4tD@carbon.dhcp.thefacebook.com>
Date:   Tue, 2 Mar 2021 12:37:59 -0800
From:   Roman Gushchin <guro@...com>
To:     Michal Hocko <mhocko@...e.com>
CC:     Muchun Song <songmuchun@...edance.com>, <hannes@...xchg.org>,
        <akpm@...ux-foundation.org>, <shakeelb@...gle.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: memcontrol: fix kernel stack account

On Tue, Mar 02, 2021 at 08:33:20PM +0100, Michal Hocko wrote:
> On Tue 02-03-21 10:50:32, Roman Gushchin wrote:
> > On Tue, Mar 02, 2021 at 03:37:33PM +0800, Muchun Song wrote:
> > > The alloc_thread_stack_node() cannot guarantee that allocated stack pages
> > > are in the same node when CONFIG_VMAP_STACK. Because we do not specify
> > > __GFP_THISNODE to __vmalloc_node_range(). Fix it by caling
> > > mod_lruvec_page_state() for each page one by one.
> > 
> > Hm, I actually wonder if it makes any sense to split the stack over multiple
> > nodes? Maybe we should fix this instead?
> 
> While this is not really ideal I am not really sure it is an actual
> problem worth complicating the code. I am pretty sure this would grow
> into more tricky problem quite quickly (e.g. proper memory policy
> handling).

I'd agree and IMO accounting a couple of pages to a different node
is even a smaller problem.