Dear David, dear Daniel,
Am 03.12.20 um 21:58 schrieb Daniel Jordan:
David Hildenbrand writes:
On 03.12.20 13:52, Paul Menzel wrote:
Am 03.12.20 um 13:25 schrieb David Hildenbrand:
On 03.12.20 11:51, Paul Menzel wrote:
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)).
[…]
We do have deferred meminit in the kernel during boot that can
initialize memory in parallel.
Is that used automatically, or do I need to activate it somehow?
If your kernel is compiled with
CONFIG_DEFERRED_STRUCT_PAGE_INIT
it should be enabled automatically.
[…]
Yes, in Debian’s Linux kernel configuration, that option is selected.
If it is enabled, what does
dmesg | grep 'deferred pages'
give you?
$ grep 'deferred pages' dmesg-full.txt
[ 0.140199] node 0 deferred pages initialised in 40ms
$ grep 'deferred pages' dmesg-2g.txt
[ 0.077892] node 0 deferred pages initialised in 4ms
And assuming you're running systemd, what does systemd-analyze show you?
Please find it below. In my experience, unpacking the initrd is also
good measurement point, and the time to write protect the kernel
read-only data.
Without `mem=` (32 GB):
$ dmesg
[…]
[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-3-amd64
root=UUID=d23ce27e-5c5c-45fb-bfa8-79a87caff13f ro quiet
cryptomgr.notests ipv6.disable=1 log_buf_len=2M initcall_debug
init=/lib/systemd/systemd-bootchart
[…]
[ 0.266513] Trying to unpack rootfs image as initramfs...
[ 0.275829] Freeing initrd memory: 4468K
[…]
[ 0.295890] Freeing unused kernel image (initmem) memory: 1640K
[ 0.335585] Write protecting the kernel read-only data: 18432k
[ 0.336261] Freeing unused kernel image (text/rodata gap)
memory: 2044K
[ 0.336406] Freeing unused kernel image (rodata/data gap)
memory: 292K
[ 0.392213] x86/mm: Checked W+X mappings: passed, no W+X pages
found.
[ 0.392213] x86/mm: Checking user space page tables
[ 0.432697] x86/mm: Checked W+X mappings: passed, no W+X pages
found.
[ 0.432701] Run /init as init process
[…]
$ systemd-analyze time
Startup finished in 3.792s (firmware) + 4.116s (loader) + 767ms
(kernel) + 1.414s (userspace) = 10.091s
graphical.target reached after 1.401s in userspace
With mem=2G
$ dmesg
[…]
[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-3-amd64
root=UUID=d23ce27e-5c5c-45fb-bfa8-79a87caff13f ro quiet
cryptomgr.notests ipv6.disable=1 log_buf_len=2M initcall_debug
init=/lib/systemd/systemd-bootchart mem=2G
[…]
[ 0.199720] Trying to unpack rootfs image as initramfs...
[ 0.209058] Freeing initrd memory: 4468K
[…]
[ 0.227433] Freeing unused kernel image (initmem) memory: 1640K
[ 0.253494] Write protecting the kernel read-only data: 18432k
[ 0.253898] Freeing unused kernel image (text/rodata gap)
memory: 2044K
[ 0.253987] Freeing unused kernel image (rodata/data gap)
memory: 292K
[ 0.297996] x86/mm: Checked W+X mappings: passed, no W+X pages
found.
[ 0.297997] x86/mm: Checking user space page tables
[ 0.338337] x86/mm: Checked W+X mappings: passed, no W+X pages
found.
[ 0.338341] Run /init as init process
$ sytsemd-analyze time
Startup finished in 650ms (kernel) + 3.009s (userspace) = 3.659s
graphical.target reached after 2.979s in userspace
(No idea why the firmware and loader timestamps are sometimes not
available.)
So the different memory sizes result in an almost 100 ms difference
during start-up, and initializing 32 GB results in a 30 percent longer
boottime up to starting the init process. (Unfortunately userspace and
several drivers later on take also quite some time.)
If you have ideas how to reduce the boot time of the full 32 GB, that’d
be great.
Kind regards,
Paul
