linux-kernel - Re: [PATCH 1/1] mm/memory_hotplug: Adds option to hot-add memory in ZONE

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Message-ID: <6cd8f8f753881aa14d9dfec9a018326abc1e3847.camel@linux.ibm.com>
Date:   Thu, 18 Jul 2019 13:03:42 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Pasha Tatashin <Pavel.Tatashin@...rosoft.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 1/1] mm/memory_hotplug: Adds option to hot-add memory in
 ZONE_MOVABLE

On Thu, 2019-07-18 at 08:19 -0400, Pavel Tatashin wrote:
> On Wed, Jul 17, 2019 at 10:42 PM Leonardo Bras <leonardo@...ux.ibm.com> wrote:
> > Adds an option on kernel config to make hot-added memory online in
> > ZONE_MOVABLE by default.
> > 
> > This would be great in systems with MEMORY_HOTPLUG_DEFAULT_ONLINE=y by
> > allowing to choose which zone it will be auto-onlined
> 
> 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().
> 
> When it is called from device online, mem->online_type should be -1:
> 
> if (mem->online_type < 0)
>      mem->online_type = MMOP_ONLINE_KEEP;
> 
> Change it to:
> if (mem->online_type < 0)
>      mem->online_type = MMOP_DEFAULT_ONLINE_TYPE;
> 
> 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
> 
> Could be expanded to support MMOP_ONLINE_KERNEL as well.
> 
> 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 Brás

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