linux-kernel - Re: [PATCH] mm: don't warn if the node is offlined

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Date:   Wed, 2 Nov 2022 10:36:07 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     "Zach O'Keefe" <zokeefe@...gle.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: don't warn if the node is offlined

On Wed, Nov 2, 2022 at 9:15 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Wed 02-11-22 09:03:57, Yang Shi wrote:
> > On Wed, Nov 2, 2022 at 12:39 AM Michal Hocko <mhocko@...e.com> wrote:
> > >
> > > On Tue 01-11-22 12:13:35, Zach O'Keefe wrote:
> > > [...]
> > > > This is slightly tangential - but I don't want to send a new mail
> > > > about it -- but I wonder if we should be doing __GFP_THISNODE +
> > > > explicit node vs having hpage_collapse_find_target_node() set a
> > > > nodemask. We could then provide fallback nodes for ties, or if some
> > > > node contained > some threshold number of pages.
> > >
> > > I would simply go with something like this (not even compile tested):
> >
> > Thanks, Michal. It is definitely an option. As I talked with Zach, I'm
> > not sure whether it is worth making the code more complicated for such
> > micro optimization or not. Removing __GFP_THISNODE or even removing
> > the node balance code should be fine too IMHO. TBH I doubt there would
> > be any noticeable difference.
>
> I do agree that an explicit nodes (quasi)round robin sounds over
> engineered. It makes some sense to try to target the prevalent node
> though because this code can be executed from khugepaged and therefore
> allocating with a completely different affinity than the original fault.

Yeah, the corner case comes from the node balance code, it just tries
to balance between multiple prevalent nodes, so you agree to remove it
IIRC?

> --
> Michal Hocko
> SUSE Labs