[Nix-dev] How to plug systemd-bootchart into kernel args?

[Nikolay Amiantov]

I've looked into possibility of plugging this, got a little carried away
and in the end implemented most of it [1]. I'm sorry, I don't generally
like taking fun implementing things away from people (helping is better
since it provokes learning)!

However, this is not finished yet -- generated SVGs are suspicious
because they contain no processes for me. It would be cool if you'd
finish testing this because my motivation has worn off (initially I
wanted to measure impact of different splash screen service
configurations on boot times).

However I'm happy to help, please ask questions regarding this code in
the PR! I've tried to make it as straightforward as possible.

Note that this requires a controversial change in our standard kernel
config, which means both you'd need to recompile your kernel and we'd
need to get a green light from people responsible for kernel config
decisions to get it mainlined.

1: https://github.com/NixOS/nixpkgs/pull/16902

On 07/12/2016 07:09 PM, Mateusz Czaplinski wrote:
> I'm mostly interested in analyzing what happens during systemd. I seem
> to understand systemd-bootchart should provide somewhat more detailed
> analysis of what's going on - e.g. like in
> https://wiki.apertis.org/Docs/System_startup#systemd-bootchart. I find
> the basic "systemd-analyze plot" somewhat too opaque for the noob I
> am... to tell the truth, I'd love to collect as much information as
> possible from wherever possible. E.g. some udev-related stuff looks
> highly suspicious in my plot (I have long red bar for my disk); but I
> couldn't find yet if/how it is possible to log the timing of udev
> events during boot... So, was hoping bootchart could maybe help me at
> least in some way...?
> 
> I'd be very grateful for any hints on how to plug systemd-bootstrap at
> any stage/point up to systemd start. I'm OK with patching nixpkgs (and
> `nixos-rebuild -I nixpkgs=~/nixpkgs switch`); anything is ok, though
> I'd sure be extra grateful for "style/approach" guidance which could
> result in a pull request that could be useful/make life easier for
> future users.
> 
> /Mateusz.

-- 
Nikolay.