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Message-ID: <6cd8f8f753881aa14d9dfec9a018326abc1e3847.camel@linux.ibm.com>
Subject: Re: [PATCH 1/1] mm/memory_hotplug: Adds option to hot-add memory in
 ZONE_MOVABLE
From:   Leonardo Bras <leonardo@linux.ibm.com>
To:     Pavel Tatashin <pasha.tatashin@soleen.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Michal Hocko <mhocko@suse.com>,
        Pavel Tatashin <pasha.tatashin@oracle.com>,
        =?ISO-8859-1?Q?J=E9r=F4me?= Glisse <jglisse@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Pasha Tatashin <Pavel.Tatashin@microsoft.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Date:   Thu, 18 Jul 2019 13:03:42 -0300
In-Reply-To: <CA+CK2bBu7DnG73SaBDwf9cBceNvKnZDEqA-gBJmKC9K_rqgO+A@mail.gmail.com>
References: <20190718024133.3873-1-leonardo@linux.ibm.com>
         <CA+CK2bBu7DnG73SaBDwf9cBceNvKnZDEqA-gBJmKC9K_rqgO+A@mail.gmail.com>
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On Thu, 2019-07-18 at 08:19 -0400, Pavel Tatashin wrote:
> On Wed, Jul 17, 2019 at 10:42 PM Leonardo Bras <leonardo@linux.ibm.com> w=
rote:
> > Adds an option on kernel config to make hot-added memory online in
> > ZONE_MOVABLE by default.
> >=20
> > This would be great in systems with MEMORY_HOTPLUG_DEFAULT_ONLINE=3Dy b=
y
> > allowing to choose which zone it will be auto-onlined
>=20
> This is a desired feature. From reading the code it looks to me that
> auto-selection of online method type should be done in
> memory_subsys_online().
>=20
> When it is called from device online, mem->online_type should be -1:
>=20
> if (mem->online_type < 0)
>      mem->online_type =3D MMOP_ONLINE_KEEP;
>=20
> Change it to:
> if (mem->online_type < 0)
>      mem->online_type =3D MMOP_DEFAULT_ONLINE_TYPE;
>=20
> And in "linux/memory_hotplug.h"
> #ifdef CONFIG_MEMORY_HOTPLUG_MOVABLE
> #define MMOP_DEFAULT_ONLINE_TYPE MMOP_ONLINE_MOVABLE
> #else
> #define MMOP_DEFAULT_ONLINE_TYPE MMOP_ONLINE_KEEP
> #endif
>=20
> Could be expanded to support MMOP_ONLINE_KERNEL as well.
>=20
> Pasha

Thanks for the suggestions Pasha,

I was made aware there is a kernel boot option "movable_node" that
already creates the behavior I was trying to reproduce.

I was thinking of changing my patch in order to add a config option
that makes this behavior default (i.e. not need to pass it as a boot
parameter.

Do you think that it would still be a desired feature?

Regards,

Leonardo Br=C3=A1s

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