linux-kernel - Re: [RFC] Disable auto_movable

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Message-ID: <ac7add36-808d-4883-a09e-ef1bf6fd6834@suse.de>
Date: Tue, 29 Jul 2025 09:24:37 +0200
From: Hannes Reinecke <hare@...e.de>
To: David Hildenbrand <david@...hat.com>, Michal Hocko <mhocko@...e.com>
Cc: Oscar Salvador <osalvador@...e.de>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...nel.org>
Subject: Re: [RFC] Disable auto_movable_ratio for selfhosted memmap

On 7/28/25 15:08, David Hildenbrand wrote:
> On 28.07.25 15:06, Michal Hocko wrote:
>> On Mon 28-07-25 11:37:46, Hannes Reinecke wrote:
>>> On 7/28/25 11:10, David Hildenbrand wrote:
>>> And to make matters worse, we have two competing user-space programs:
>>> - udev
>>> - daxctl
>>> neither of which is (or can be made) aware of each other.
>>> This leads to races and/or inconsistencies.
>>
>> Would it help if generic udev memory hotplug rule exclude anything that
>> is dax backed? Is there a way to check for that? Sorry if this is a
>> stupid question.
> Parsing /proc/iomem, it's indicated as "System RAM (kmem)".
> 
I would rather do it the other way round, and make daxctl aware of
udev. In the end, even 'daxctl' uses the sysfs interface to online
memory, which really is the territory of udev and can easily be
done via udev rules (for static configuration).

Note, we do a similar thing on s/390; the configuration tool there
just spits out udev rules.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich