From: Paul Menzel <pmenzel@molgen.mpg.de>
To: Feng Tang <feng.tang@intel.com>
Cc: linux-mm@kvack.org, Arjan van de Ven <arjan@linux.intel.com>
Subject: Deferred Memory Init: How to bring rest of memory online after limiting it with `mem=XG`?
Date: Thu, 3 Dec 2020 11:51:58 +0100 [thread overview]
Message-ID: <b7cd0584-0fd4-a926-b254-273943504293@molgen.mpg.de> (raw)
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
Starting Linux with `mem=2G` indeed reduces the startup time, but I am
unable to get the rest of the memory online. Comparing it with a boot
without `mem=2G` the `memoryX` devices under
`/sys/devices/system/memory/` are missing.
With `mem=2G`:
$ lsmem --output-all
RANGE SIZE STATE REMOVABLE BLOCK NODE
ZONES
0x0000000000000000-0x0000000007ffffff 128M online yes 0 0
None
0x0000000008000000-0x000000007fffffff 1,9G online yes 1-15 0
DMA32
Memory block size: 128M
Total online memory: 2G
Total offline memory: 0B
$ ls -d /sys/devices/system/memory/memory*
/sys/devices/system/memory/memory0 /sys/devices/system/memory/memory2
/sys/devices/system/memory/memory1 /sys/devices/system/memory/memory3
/sys/devices/system/memory/memory10 /sys/devices/system/memory/memory4
/sys/devices/system/memory/memory11 /sys/devices/system/memory/memory5
/sys/devices/system/memory/memory12 /sys/devices/system/memory/memory6
/sys/devices/system/memory/memory13 /sys/devices/system/memory/memory7
/sys/devices/system/memory/memory14 /sys/devices/system/memory/memory8
/sys/devices/system/memory/memory15 /sys/devices/system/memory/memory9
```
Without `mem=2G`:
```
$ lsmem --output-all
RANGE SIZE STATE REMOVABLE BLOCK NODE
ZONES
0x0000000000000000-0x0000000007ffffff 128M online yes 0 0
None
0x0000000008000000-0x0000000087ffffff 2G online yes 1-16 0
DMA32
0x0000000088000000-0x000000008fffffff 128M online yes 17 0
None
0x0000000100000000-0x0000000867ffffff 29,6G online yes 32-268 0
Normal
0x0000000868000000-0x000000086fffffff 128M online yes 269 0
None
Memory block size: 128M
Total online memory: 32G
Total offline memory: 0B
```
Can the deferred memory initialization be done with the upstream Linux
kernel, or were you using patches on top?
Kind regards,
Paul
[1]:
https://www.linuxplumbersconf.org/event/4/contributions/281/attachments/216/617/LPC_2019_kernel_fastboot_on_the_way.pdf
next reply other threads:[~2020-12-03 10:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 10:51 Paul Menzel [this message]
2020-12-03 12:25 ` Deferred Memory Init: How to bring rest of memory online after limiting it with `mem=XG`? David Hildenbrand
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b7cd0584-0fd4-a926-b254-273943504293@molgen.mpg.de \
--to=pmenzel@molgen.mpg.de \
--cc=arjan@linux.intel.com \
--cc=feng.tang@intel.com \
--cc=linux-mm@kvack.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.