linux-kernel - Re: [PATCH v2] mm/page_alloc: Dedupe some memcg uncharging logic

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Date:   Wed, 8 Nov 2023 16:07:21 -0800
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Brendan Jackman <jackmanb@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] mm/page_alloc: Dedupe some memcg uncharging logic

On Wed, Nov 8, 2023 at 3:52 PM Shakeel Butt <shakeelb@...gle.com> wrote:
>
> On Wed, Nov 8, 2023 at 8:49 AM Brendan Jackman <jackmanb@...gle.com> wrote:
> >
> > The duplication makes it seem like some work is required before
> > uncharging in the !PageHWPoison case. But it isn't, so we can simplify
> > the code a little.
> >
> > Note the PageMemcgKmem check is redundant, but I've left it in as it
> > avoids an unnecessary function call.
> >
> > Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
>
> Thanks for the patch. Actually the PageMemcgKmem/folio_memcg_kmem
> check should be in memcg_kmem_uncharge_page() and not in
> __memcg_kmem_uncharge_page(). Anyways, that is orthogonal to this
> patch.

Agreed. If we move the check into memcg_kmem_uncharge_page(), perhaps
we should call it directly here instead of doing the checks, since
there won't be an extra function call as it is inline, right? We can
also make __memcg_kmem_uncharge_page static to mm/memcontrol.c

I suspect the same can be done for __memcg_kmem_charge_page() as well.