From: "Huang, Ying" <email@example.com>
To: Oscar Salvador <firstname.lastname@example.org>
Cc: Andrew Morton <email@example.com>,
Dave Hansen <firstname.lastname@example.org>,
Abhishek Goel <email@example.com>,
Baolin Wang <firstname.lastname@example.org>,
Subject: Re: [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N_CPU state
Date: Mon, 14 Mar 2022 09:03:59 +0800 [thread overview]
Message-ID: <email@example.com> (raw)
In-Reply-To: <YisK2PEkKAqtZPfp@localhost.localdomain> (Oscar Salvador's message of "Fri, 11 Mar 2022 09:39:52 +0100")
Oscar Salvador <firstname.lastname@example.org> writes:
> On Fri, Mar 11, 2022 at 10:24:07AM +0800, Huang, Ying wrote:
>> It may be unnecessary to be fixed in this patch. But I think we need to
>> cleanup the kernel config dependencies of the demotion code at some time.
> I am glad you brought this up because it is something I have been
> thinking about.
> I already added it in my to-do list, but I would do it in a separate
> patch if you do not mind.
> Now, let us try to untangle this mess:
>> 1. Even if !defined(CONFIG_HOTPLUG_CPU) &&
>> !defined(CONFIG_MEMORY_HOTPLUG), we still need to allocate
>> "node_demotion" and call set_migration_target_nodes() during boot time.
>> 2. If !defined(CONFIG_MEMORY_HOTPLUG), we don't need
>> 3. We need defined(CONFIG_NUMA) && defined(CONFIG_MIGRATION) for all
>> these code.
> Back in the early versions  I asked whether we could have some
> scenario where this feature could be used when !CONFIG_MEMORY_HOTPLUG
> The reason I was given is that in order to bind the expose PMEM memory
> as RAM (add_memory_driver_managed()), we need MEMORY_HOTPLUG.
> Now, as I said back then, I am not sure whether PMEM memory can be
> exposed as RAM by other means, but as it was pointed out back then,
> it really looks like we, at least, need CONFIG_MEMORY_HOTPLUG.
> Ok, so we have our first dependency: CONFIG_MEMORY_HOTPLUG.
On host machine, PMEM is always exposed via memory hotplug. But later
on, we found that for guest system it's possible for PMEM to be exposed
as normal memory.
> Now, about CONFIG_HOTPLUG_CPU, it seems that that is not a strong dependency,
> as we do not need cpu-hotplug in order to use the feature.
> We definitely need CONFIG_MIGRATION and CONFIG_NUMA though.
> So, we have something like:
> - Depends:
> * CONFIG_NUMA (obvius)
> * CONFIG_MIGRATION (to migrate between nodes)
> * CONFIG_MEMORY_HOTPLUG (to expose PMEM as RAM)
> Sounds about right?
>  https://patchwork.kernel.org/project/linux-mm/patch/20210401183221.977831DE@viggo.jf.intel.com/#24099405
>  https://patchwork.kernel.org/project/linux-mm/patch/20210401183221.977831DE@viggo.jf.intel.com/#24103467
next prev parent reply other threads:[~2022-03-14 1:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-10 12:07 [PATCH v2] mm: Only re-generate demotion targets when a numa node changes its N_CPU state Oscar Salvador
2022-03-11 1:33 ` Baolin Wang
2022-03-11 2:24 ` Huang, Ying
2022-03-11 8:39 ` Oscar Salvador
2022-03-14 1:03 ` Huang, Ying [this message]
2022-03-14 15:13 ` Oscar Salvador
2022-03-14 15:20 ` Dave Hansen
2022-03-15 6:13 ` Oscar Salvador
2022-03-15 6:31 ` Huang, Ying
2022-03-11 2:39 ` Andrew Morton
2022-03-11 9:23 ` Oscar Salvador
2022-03-11 17:10 ` Dave Hansen
2022-03-14 9:09 ` Abhishek Goel
2022-03-11 5:06 ` Huang, Ying
2022-03-11 9:17 ` Oscar Salvador
2022-03-14 3:09 ` Huang, Ying
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