why lsb_release looks slower than a program supposed to print few bytes?

Question

i'm just wondering why in all linux boxs , lsb_release take longer time to print few infos about distro,
anyone could enlighten me about this fact ? please.

Answer 1

Printing a few bytes isn't the difficult part. The difficult part is finding what bytes should be printed. To do that, lsb_release needs to analyze many system files. You can see where it's spending time in I/O by tracing its system calls:

strace -f -tt -T -o lsb_release.strace lsb_release

On my machine, about 1/3 of the time is spent executing the command

dpkg-query -f '${Version} ${Provides}\n' -W lsb-core lsb-cxx lsb-graphics lsb-desktop lsb-languages lsb-multimedia lsb-printing lsb-security

which parses the database of installed packages. There isn't another significant I/O consumer.

Since this is a Python script, you can also use the Python profiler to get an idea of where it's spending time:

python -m cProfile

This isn't very revealing to me, the biggest time consumers are related to the initialization of the script (it does use quite a few libraries) and to the invocation of the dpkg subprocess.