On 10/26/24 02:36, Saravana Kannan wrote:
On Fri, Oct 25, 2024 at 11:18 AM Bird, Tim <Tim.Bird@xxxxxxxx> wrote:
Hey Linux developers,
The response to my request to form a Special Interest Group for boot-time reduction
for Linux has been really great. Many people contacted me by e-mail and on LinkedIn.
Hi Tim,
Thanks for organizing this and moving it forward! I'd be interested in
contributing to this effort as a lot of work I have done aligns with
the goals of this effort and boot time is of obvious value to Android.
I'm kind of an edge case for this project because my mkroot images at
https://landley.net/bin/mkroot/latest mostly boot up in a couple
seconds. (And faster if you feed in KARGS=quiet so the kernel boot
messages don't take time emitting and scrolling before interrupts have
been enabled. Although "quiet" doesn't seem to work in current vanilla
kernels...?)
The ones that _don't_ are generally because qemu's bios for that
platform twiddles its thumbs for a long time before launching the
kernel, although there are some slow drivers in there:
$ for i in powerpc m68k i686 s390x; do (cd $i && echo $i && KARGS='quiet
HANDOFF=echo' bash -c 'time ./run-qemu.sh > /dev/null'); done
powerpc
real 0m6.154s
user 0m3.689s
sys 0m0.341s
m68k
real 0m4.220s
user 0m1.142s
sys 0m0.212s
i686
real 0m1.986s
user 0m1.709s
sys 0m0.209s
s390x
real 0m1.644s
user 0m1.378s
sys 0m0.228s
And that's with qemu running on a 10 year old laptop that I'll have to
switch off of when debian drops x86-64-v2 support. (Even that i686 test
isn't kvm.) It's running a recent-ish kernel (binaries I had lying
around)...
# cat /proc/version
Linux version 6.11.0-rc7 (landley@driftwood) (s390x-linux-musl-gcc (GCC)
11.4.0, GNU ld (GNU Binutils) 2.33.1) #1 SMP Sat Sep 14 01:36:19 CDT 2024
Built using the kernel config files in the "doc" directory of those
tarballs.
Are you trying to optimize the kernel boot, or more trying to optimize
userspace? Because my userspace init is just a small shell script:
https://github.com/landley/toybox/blob/master/mkroot/mkroot.sh#L102
And the above simple test loop just told that to run "echo" instead of
/bin/sh so I could easily collect boot-and-exit timing for the qemu
process...
I had hoped to push out a script today to start to gather data on boot-time on different
platforms, for people to run who had expressed interest in helping with this effort. But
I got overwhelmed with other tasks, and I may not get it done today. I'll be in Tokyo next
week for Open Source Summit Japan. If you are there, please try to catch me and say hi.
Given that, I'll see how soon I can provide the script I'm talking about, and we can
discuss the goals and design of the script.
I regression test under qemu because it gives reproducibly scriptable
results. I've even got plumbing to run canned tests on multiple
architectures in parallel (part of my release testing):
https://github.com/landley/toybox/blob/master/mkroot/testroot.sh
Rob
