From: David Hildenbrand <david@redhat.com>
To: Paul Menzel <pmenzel@molgen.mpg.de>, Feng Tang <feng.tang@intel.com>
Cc: linux-mm@kvack.org, Arjan van de Ven <arjan@linux.intel.com>
Subject: Re: Deferred Memory Init: How to bring rest of memory online after limiting it with `mem=XG`?
Date: Thu, 3 Dec 2020 13:25:04 +0100 [thread overview]
Message-ID: <808e493f-18a2-fe82-46b3-e44fe87e989c@redhat.com> (raw)
In-Reply-To: <b7cd0584-0fd4-a926-b254-273943504293@molgen.mpg.de>
On 03.12.20 11:51, Paul Menzel wrote:
> Dear Feng,
>
>
> I am trying to reduce the startup time of Debian’s Linux 5.9.9 on a
> Intel Kaby Lake system with 32 GB of memory (TUXEDO Book BU1406 (Clevo
> N240BU)). On your Linux Plumbers Conference 2019 slides of your talk
> *Linux Kernel Fastboot On the Way* [1], you mention *Deferred Memory Init*:
>
>> Deferred Memory Init
>>
>> • 8GB RAM’s initialization costs 100+ ms
>> • In early boot phase, we don’t need that much memory
>> • Utilize the memory hotplug feature
>> • “mem=4096m” in cmdline to only init 2 GB
>> • Use systemd service to add rest memory in parallel
Uh, that sounds very wrong and flawed.
Even if you would be adding+onlining memory in parallel, memory
hotplug/onlining code runs strictly sequential. This does not work.
And I question this approach in general.
We do have deferred meminit in the kernel during boot that can
initialize memory in parallel.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-12-03 12:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 10:51 Deferred Memory Init: How to bring rest of memory online after limiting it with `mem=XG`? Paul Menzel
2020-12-03 12:25 ` David Hildenbrand [this message]
2020-12-03 12:52 ` Paul Menzel
2020-12-03 13:06 ` David Hildenbrand
2020-12-03 20:58 ` Daniel Jordan
2020-12-04 7:31 ` Paul Menzel
2020-12-04 19:50 ` Daniel Jordan
2020-12-04 1:17 ` Feng Tang
2020-12-04 8:05 ` Feng Tang
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