linux-kernel - Re: [PATCH 2/9] mm: vmscan: use nid from shrink

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Date:   Fri, 11 Dec 2020 11:20:19 -0800
From:   Yang Shi <shy828301@...il.com>
To:     "Xiaqing (A)" <saberlily.xia@...ilicon.com>
Cc:     Roman Gushchin <guro@...com>, Kirill Tkhai <ktkhai@...tuozzo.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Liu Yi <daniel.liuyi@...ilicon.com>
Subject: Re: [PATCH 2/9] mm: vmscan: use nid from shrink_control for tracepoint

On Wed, Dec 2, 2020 at 7:13 PM Xiaqing (A) <saberlily.xia@...ilicon.com> wrote:
>
>
>
> On 2020/12/3 2:27, Yang Shi wrote:
> > The tracepoint's nid should show what node the shrink happens on, the start tracepoint
> > uses nid from shrinkctl, but the nid might be set to 0 before end tracepoint if the
> > shrinker is not NUMA aware, so the traceing log may show the shrink happens on one
> > node but end up on the other node.  It seems confusing.  And the following patch
> > will remove using nid directly in do_shrink_slab(), this patch also helps cleanup
> > the code.
> >
> > Signed-off-by: Yang Shi <shy828301@...il.com>
> > ---
> >   mm/vmscan.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 7d6186a07daf..457ce04eebf2 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -533,7 +533,7 @@ static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
> >       new_nr = atomic_long_add_return(next_deferred,
> >                                       &shrinker->nr_deferred[nid]);
> >
> > -     trace_mm_shrink_slab_end(shrinker, nid, freed, nr, new_nr, total_scan);
> > +     trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
>
> Hi， Yang
>
> When I read this patch, I wondered why you modified it so much until I read patch6. Could you merge
> this patch into patch6?

Sorry for the late reply. It could be, but I was inclined to think
this is a bug and we might need backport it to stable, so I leave it
as a standalone patch.

>
> Thanks!
>
> >       return freed;
> >   }
> >
>