.. Copyright (C) ALbert Mietus, 2026

.. image:: images/ScalingBig-1.png

.. _CodeXorArchitect-scalingbig-1:

Scaling Big (1)
===============

.. post:: 15/Sept 2026
   :tags: CodeXorArchitect
   :category: LinkedIn-Post

   :reading-time:	1m17
   :LinkedIn: 		https://lnkd.in/p/ex67jcaB


   You shouldn't build a 350m-high skyscraper like a bike shed; likewise, Linux (35M lines of code) needed a different
   principle than ``HelloWorld``.  All software starts small, though. Once, Linux fit on a single page.
   |BR|
   Architecture helps to scale! E.g., Linux is based on the *'Common Unix Architecture'*, with drivers, CPU abstraction,
   file- & networking-I/O, etc. Even version v0.0.1 of the Linux kernel used it.

Remember, a big codebase is a lot of work. Estimates suggest a product of Linux's complexity costs around **20,000 Sprints**.
|BR|
But it always starts small and smooth; you probably know every line of ``HelloWorld``. But that approach doesn't
scale -- you can't memorize 35M Source Lines of Code.

To scale, no single software engineer should ever get lost in a codebase. Otherwise nobody can add features, and the
system can't grow!

Grouping sources in (sub)directories along the architectural structure helps!
|BR|
Roughly, 80% of all Linux code is in the `drivers` directory. When you're not working on drivers, you can skip the biggest
portion of the code in a heartbeat. This structure is everywhere.  To improve, for example, the real-time behaviour of the
‘scheduler’, you can also skip the hardware abstraction and all I/O modules. Only about 0.2% of all code is for the
scheduler, and it's easy to find (in ``/kernel/sched/`` :-).
|BR|
The real-time part of the scheduler is even smaller; it's less than 1/100 of 1% of the codebase: a manageable 2k lines.

Architecture should bring structure, the ability to find stuff, and the benefit of changing a few lines without
reading most of the code. It enables scaling your teams.
|BR|
Next time you start coding something that can grow beyond 5 lines: Start with a sound architecture. Always make sure
there is only one logical spot for all future lines. Then, one day, you can add as many SW-bricklayers as you need for
your “skyscraper”.

..  LocalWords:  codebase