linux-kernel - Re: [PATCH v3 2/3] mm: vmscan: refactor updating reclaimed pages in reclaim

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Message-ID: <CAJD7tkai_tv32GREjLvopLkUufq+WiR0-fFr-eNAzZNmQqk5dQ@mail.gmail.com>
Date:   Fri, 31 Mar 2023 15:11:46 -0700
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Dave Chinner <david@...morbit.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Hildenbrand <david@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Peter Xu <peterx@...hat.com>, NeilBrown <neilb@...e.de>,
        Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 2/3] mm: vmscan: refactor updating reclaimed pages in reclaim_state

On Fri, Mar 31, 2023 at 1:51 PM Dave Chinner <david@...morbit.com> wrote:
>
> On Fri, Mar 31, 2023 at 07:08:17AM +0000, Yosry Ahmed wrote:
> > During reclaim, we keep track of pages reclaimed from other means than
> > LRU-based reclaim through scan_control->reclaim_state->reclaimed_slab,
> > which we stash a pointer to in current task_struct.
> >
> > However, we keep track of more than just reclaimed slab pages through
> > this. We also use it for clean file pages dropped through pruned inodes,
> > and xfs buffer pages freed. Rename reclaimed_slab to reclaimed, and add
> > a helper function that wraps updating it through current, so that future
> > changes to this logic are contained within mm/vmscan.c.
> >
> > Signed-off-by: Yosry Ahmed <yosryahmed@...gle.com>
> .....
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index fef7d1c0f82b2..a3e38851b34ac 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -511,6 +511,34 @@ static void set_task_reclaim_state(struct task_struct *task,
> >       task->reclaim_state = rs;
> >  }
> >
> > +/*
> > + * mm_account_reclaimed_pages(): account reclaimed pages outside of LRU-based
> > + * reclaim
> > + * @pages: number of pages reclaimed
> > + *
> > + * If the current process is undergoing a reclaim operation, increment the
> > + * number of reclaimed pages by @pages.
> > + */
> > +void mm_account_reclaimed_pages(unsigned long pages)
> > +{
> > +     if (current->reclaim_state)
> > +             current->reclaim_state->reclaimed += pages;
> > +}
> > +EXPORT_SYMBOL(mm_account_reclaimed_pages);
>
> Shouldn't this be a static inline in a header file?
>
> Then you don't need an EXPORT_SYMBOL() - which should really be
> EXPORT_SYMBOL_GPL() - and callers don't add the overhead of a
> function call for two lines of code....

Yes it should be. Thanks.

An earlier draft of this series had more going on in this function, so
I moved it to mm/vmscan.c, then I forgot to move it to the header
later. Will do that for v4.

>
> -Dave.
> --
> Dave Chinner
> david@...morbit.com