Demos¶

The programs demonstrated during the lecture, one directory per part of it.

Each demo is small on purpose: it makes one point, and it is meant to be run rather than read. The write-up in each directory says what to expect, what actually happens, and why the two differ.

Demo	Part of the lecture	What it shows
`00-pitch/`	00. Pitch	Even a bare `Hello, World!` runs mostly kernel instructions.
`01-make-os/`	01. What makes an OS	The smallest specialised OS is still hundreds of kilobytes.
`02-os-interface/`	02. The OS interface	Talking to the kernel directly, and what the crossing costs.
`03-privileged-domain/`	03. Privileged domains	Privileged instructions fault in user mode; the boundary is in silicon.
`04-optimize-os-interface/`	04. Optimizing the interface	Two ways to pay the system-call tax less: buffering, and `sendfile()`.

Running them¶

Every demo that needs building has a Makefile, so make inside its directory is enough. The tools the demos need, beyond a C compiler and make, are:

nasm and ld, for the assembly programs in 00-pitch/, 02-os-interface/ and 03-privileged-domain/
perf (linux-tools), to count retired instructions -- needs sudo
strace, to see the system calls a program makes
docker or a QEMU/Unikraft toolchain, for 01-make-os/ (see its README for the full requirement list)

perf is the only hard dependency beyond the compiler toolchain, and only the instruction-count outputs need it; the timings print without it.