os_info shouldn't call out to external commands on Linux (it is slow)

[VorpalBlade]

I have a program that runs for a very short time (<100 ms), that needs to know what Linux distro it is on. Unfortunately using os_info results in a lot of (relative) overhead due to it calling out to external binaries. About 35 ms extra in fact. The program runtime is performance criticial, it gets invoked many times from a shell script.

It seems that lsb_release is the worst offender (at ~35 ms). Removing lsb_release from path brings the overhead down to a more manageble ~4-5 ms. There is an old issue #319 about this, but no progress.

The remaining invoked programs seem to be:

• getconf
• uname
• Somehow reinvoking the program itself? At least it looks like that in perf/hotspot:
  

Both getconf and uname should be possible to replace with calls to nix, libc or even rustix.

I have no idea why it looks like os_info is reivoking my program (paketkoll) though. But that shouldn't be needed either really. And yes, that extra process goes away if I remove os_info (and hard code in what distro is in use, in this case Arch Linux).

[stanislav-tkach]

I agree with your concerns, but unfortunately I don't have time right now to fix that. Hopefully I will be able to look into that in about a month, but I don't want to promise anything. I welcome pull requests if you would like to implement that yourself.

[ydirson]

I would argue that a frequently-running tool does not really need to call os_info every time, since that info is unlikely to change. Even if it would avoid calling lsb_release it would do extra work you don't need.
I suggest caching the info you need in /run