From: David Hildenbrand <david@redhat.com>
To: Roger Pau Monne <roger.pau@citrix.com>, linux-kernel@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
xen-devel@lists.xenproject.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/3] memory: introduce an option to force onlining of hotplug memory
Date: Thu, 23 Jul 2020 13:37:03 +0200 [thread overview]
Message-ID: <21490d49-b2cf-a398-0609-8010bdb0b004@redhat.com> (raw)
In-Reply-To: <20200723084523.42109-4-roger.pau@citrix.com>
On 23.07.20 10:45, Roger Pau Monne wrote:
> Add an extra option to add_memory_resource that overrides the memory
> hotplug online behavior in order to force onlining of memory from
> add_memory_resource unconditionally.
>
> This is required for the Xen balloon driver, that must run the
> online page callback in order to correctly process the newly added
> memory region, note this is an unpopulated region that is used by Linux
> to either hotplug RAM or to map foreign pages from other domains, and
> hence memory hotplug when running on Xen can be used even without the
> user explicitly requesting it, as part of the normal operations of the
> OS when attempting to map memory from a different domain.
>
> Setting a different default value of memhp_default_online_type when
> attaching the balloon driver is not a robust solution, as the user (or
> distro init scripts) could still change it and thus break the Xen
> balloon driver.
I think we discussed this a couple of times before (even triggered by my
request), and this is responsibility of user space to configure. Usually
distros have udev rules to online memory automatically. Especially, user
space should eb able to configure *how* to online memory.
It's the admin/distro responsibility to configure this properly. In case
this doesn't happen (or as you say, users change it), bad luck.
E.g., virtio-mem takes care to not add more memory in case it is not
getting onlined. I remember hyper-v has similar code to at least wait a
bit for memory to get onlined.
Nacked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
WARNING: multiple messages have this Message-ID (diff)
From: David Hildenbrand <david@redhat.com>
To: Roger Pau Monne <roger.pau@citrix.com>, linux-kernel@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>,
Stefano Stabellini <sstabellini@kernel.org>,
linux-mm@kvack.org, xen-devel@lists.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 3/3] memory: introduce an option to force onlining of hotplug memory
Date: Thu, 23 Jul 2020 13:37:03 +0200 [thread overview]
Message-ID: <21490d49-b2cf-a398-0609-8010bdb0b004@redhat.com> (raw)
In-Reply-To: <20200723084523.42109-4-roger.pau@citrix.com>
On 23.07.20 10:45, Roger Pau Monne wrote:
> Add an extra option to add_memory_resource that overrides the memory
> hotplug online behavior in order to force onlining of memory from
> add_memory_resource unconditionally.
>
> This is required for the Xen balloon driver, that must run the
> online page callback in order to correctly process the newly added
> memory region, note this is an unpopulated region that is used by Linux
> to either hotplug RAM or to map foreign pages from other domains, and
> hence memory hotplug when running on Xen can be used even without the
> user explicitly requesting it, as part of the normal operations of the
> OS when attempting to map memory from a different domain.
>
> Setting a different default value of memhp_default_online_type when
> attaching the balloon driver is not a robust solution, as the user (or
> distro init scripts) could still change it and thus break the Xen
> balloon driver.
I think we discussed this a couple of times before (even triggered by my
request), and this is responsibility of user space to configure. Usually
distros have udev rules to online memory automatically. Especially, user
space should eb able to configure *how* to online memory.
It's the admin/distro responsibility to configure this properly. In case
this doesn't happen (or as you say, users change it), bad luck.
E.g., virtio-mem takes care to not add more memory in case it is not
getting onlined. I remember hyper-v has similar code to at least wait a
bit for memory to get onlined.
Nacked-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-07-23 11:37 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 8:45 [PATCH 0/3] xen/balloon: fixes for memory hotplug Roger Pau Monne
2020-07-23 8:45 ` [PATCH 1/3] xen/balloon: fix accounting in alloc_xenballooned_pages error path Roger Pau Monne
2020-07-23 8:45 ` Roger Pau Monne
2020-07-23 8:45 ` [PATCH 2/3] xen/balloon: make the balloon wait interruptible Roger Pau Monne
2020-07-23 8:45 ` Roger Pau Monne
2020-07-23 8:45 ` [PATCH 3/3] memory: introduce an option to force onlining of hotplug memory Roger Pau Monne
2020-07-23 8:45 ` Roger Pau Monne
2020-07-23 11:37 ` David Hildenbrand [this message]
2020-07-23 11:37 ` David Hildenbrand
2020-07-23 11:52 ` David Hildenbrand
2020-07-23 11:52 ` David Hildenbrand
2020-07-23 12:23 ` Roger Pau Monné
2020-07-23 12:23 ` Roger Pau Monné
2020-07-23 12:28 ` Jürgen Groß
2020-07-23 12:28 ` Jürgen Groß
2020-07-23 12:31 ` David Hildenbrand
2020-07-23 12:31 ` David Hildenbrand
2020-07-23 13:08 ` Roger Pau Monné
2020-07-23 13:08 ` Roger Pau Monné
2020-07-23 13:14 ` David Hildenbrand
2020-07-23 13:14 ` David Hildenbrand
2020-07-23 13:25 ` Roger Pau Monné
2020-07-23 13:25 ` Roger Pau Monné
2020-07-23 13:20 ` Jürgen Groß
2020-07-23 13:20 ` Jürgen Groß
2020-07-23 13:39 ` Roger Pau Monné
2020-07-23 13:39 ` Roger Pau Monné
2020-07-23 13:49 ` Jürgen Groß
2020-07-23 13:49 ` Jürgen Groß
2020-07-23 13:22 ` David Hildenbrand
2020-07-23 13:22 ` David Hildenbrand
2020-07-23 13:47 ` David Hildenbrand
2020-07-23 13:47 ` David Hildenbrand
2020-07-23 13:53 ` Jürgen Groß
2020-07-23 13:53 ` Jürgen Groß
2020-07-23 13:59 ` Roger Pau Monné
2020-07-23 13:59 ` Roger Pau Monné
2020-07-23 15:10 ` Jürgen Groß
2020-07-23 15:10 ` Jürgen Groß
2020-07-23 16:03 ` Andrew Cooper
2020-07-23 16:03 ` Andrew Cooper
2020-07-23 16:22 ` Roger Pau Monné
2020-07-23 16:22 ` Roger Pau Monné
2020-07-23 17:39 ` David Hildenbrand
2020-07-23 17:39 ` David Hildenbrand
2020-07-24 7:28 ` Michal Hocko
2020-07-24 7:28 ` Michal Hocko
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