Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1594107889-32228-1-git-send-email-iamjoonsoo.kim@lge.com>
 <1594107889-32228-12-git-send-email-iamjoonsoo.kim@lge.com> <575ab75d-1382-5f12-96df-53c0bb947f8c@suse.cz>
In-Reply-To: <575ab75d-1382-5f12-96df-53c0bb947f8c@suse.cz>
From:   Joonsoo Kim <js1304@gmail.com>
Date:   Thu, 9 Jul 2020 12:25:30 +0900
Message-ID: <CAAmzW4MdTstiqEccFsw61HHyim2uutA8jd23reX-kOtDnXmzDQ@mail.gmail.com>
Subject: Re: [PATCH v4 11/11] mm/memory_hotplug: remove a wrapper for alloc_migration_target()
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, kernel-team@lge.com,
        Christoph Hellwig <hch@infradead.org>,
        Roman Gushchin <guro@fb.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Michal Hocko <mhocko@suse.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

2020=EB=85=84 7=EC=9B=94 8=EC=9D=BC (=EC=88=98) =EC=98=A4=EC=A0=84 1:34, Vl=
astimil Babka <vbabka@suse.cz>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> On 7/7/20 9:44 AM, js1304@gmail.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> > To calculate the correct node to migrate the page for hotplug, we need
> > to check node id of the page. Wrapper for alloc_migration_target() exis=
ts
> > for this purpose.
> >
> > However, Vlastimil informs that all migration source pages come from
> > a single node. In this case, we don't need to check the node id for eac=
h
> > page and we don't need to re-set the target nodemask for each page by
> > using the wrapper. Set up the migration_target_control once and use it =
for
> > all pages.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>
> Thanks! Nitpick below.
>
> > @@ -1345,9 +1324,28 @@ do_migrate_range(unsigned long start_pfn, unsign=
ed long end_pfn)
> >               put_page(page);
> >       }
> >       if (!list_empty(&source)) {
> > -             /* Allocate a new page from the nearest neighbor node */
> > -             ret =3D migrate_pages(&source, new_node_page, NULL, 0,
> > -                                     MIGRATE_SYNC, MR_MEMORY_HOTPLUG);
> > +             nodemask_t nmask =3D node_states[N_MEMORY];
> > +             struct migration_target_control mtc =3D {
> > +                     .nmask =3D &nmask,
> > +                     .gfp_mask =3D GFP_USER | __GFP_MOVABLE | __GFP_RE=
TRY_MAYFAIL,
> > +             };
> > +
> > +             /*
> > +              * We have checked that migration range is on a single zo=
ne so
> > +              * we can use the nid of the first page to all the others=
.
> > +              */
> > +             mtc.nid =3D page_to_nid(list_first_entry(&source, struct =
page, lru));
> > +
> > +             /*
> > +              * try to allocate from a different node but reuse this n=
ode
> > +              * if there are no other online nodes to be used (e.g. we=
 are
> > +              * offlining a part of the only existing node)
> > +              */
> > +             node_clear(mtc.nid, *mtc.nmask);
> > +             if (nodes_empty(*mtc.nmask))
> > +                     node_set(mtc.nid, *mtc.nmask);
>
> You could have kept using 'nmask' instead of '*mtc.nmask'. Actually that =
applies
> to patch 6 too, for less churn.

You are right. I will change it.

Thanks.