[systemd-devel] Q: Reducing systemd Userspace Boot Time Below 2 Seconds on Minimal Embedded ARM Board

[Michal Koutný]

Hello Dharma.

What a challenge!

On Fri, Jul 18, 2025 at 05:51:39AM +0000, Dharma.B at microchip.com wrote:
> I've reviewed
> systemd.io/OPTIMIZATIONS<https://systemd.io/OPTIMIZATIONS/> and
> applied all recommendations relevant to my scenario (disabling settle
> services, removing legacy storage stacks, fixing locale, etc.).
> Question:
> Given the above, is it realistic to further reduce systemd userspace
> boot time below 2 seconds on such an SD-boot, minimal embedded board?

IIUC, your main workload is hmi.service. It looks like its startup is
the main contributor to the boot time. You may learn simply from journal
what are the events that it waits for.


> Are there advanced tunables, overlooked dependencies, or
> hardware-specific factors I should consider to claw back a few hundred
> milliseconds? Any experience or pointers—especially from similar
> setups—are very welcome.

I can certainly recommend Brendan Gregg's materials on on-cpu profiling
[1] (in case your boot is CPU bound) or off-cpu profiling [2] (in case
it's IO or parallelization issue). Though you may need to customize your
build to make the infrastructure working (and risk observer impact :-/).

Good luck,
Michal

[1] https://www.brendangregg.com/FlameGraphs/cpuflamegraphs.html
[2] https://www.brendangregg.com/offcpuanalysis.html
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