note: this was mostly written in July 2015 and promptly forgotten about. I stumbled upon it over the weekend and enjoyed reading it, so I'm publishing it now.
The worst feeling as a user of a general purpose computer is the sense that the computer is getting away from you; the sense that you're no longer in control of what's going on and don't even understand how you might regain it.
I want to be less susceptible to this feeling; I want to be empowered by the technology I use and never get bogged down by breakage in something I can't fix. I want to have a sense of mastery over and comfort in the tools that I have to use to get my job done.
One of the tools I use frequently is Vim (a tremendously complex program, but we'll get to that later. I still find the relative simplicity of my Vim setup comforting compared to that of an IDE or more complex editor). In it, the simplest and most general way to navigate the filesystem is by "fuzzy-searching" files, often scoped to the directory that Vim was launched in. This functionality isn't built in to Vim, but it's popular enough that there are many plugins that purport to provide it.
The other day, I launched Vim in one of my project directories and typed in "layout.css" to open the eponymously named file in the root of the project. Bafflingly, my fuzzy search plugin reported "no results." This wasn't complicated substring matching spread across word and path boundaries; this was a failed match of a literal text string. Okay, I'm a programmer, and this program is misbehaving... let's fix it. I jumped to the source of the plugin, opened it up to begin debugging, and... wow. I just remembered that a) I don't know vimscript and b) vimscript is an ancient, often inscrutable language, full of questionable abbreviations and syntax that seemingly grew by accretion. To add insult to injury, the plugin is three thousand lines of the stuff... even if I knew the language, could I track down the bug in a reasonable amount of time?
Thoroughly daunted, I gave up, but this episode stuck with me.
After a few weeks of this frustration gnawing at me, I reset my dev environment. When something breaks in my computer system, I want the freedom to fix it as simply and painlessly as possible. I want to be able to read the source to the tools I use day to day and fix bugs or inconsistencies in their behavior.
The more complicated a tool is, the less of a chance I give myself to comprehend or repair it when it breaks. What aspects of my toolchain would I be comfortable eliminating or "trading down" in complexity for simpler tools?
Here's some software I rely on to build programs day-to-day:
- Mac OS X: closed-source, 87 million+ lines of code
- Terminal.app: closed-source, unknown complexity
- Safari: Webkit alone is 1.8 million lines of code
- vim: ~350kloc
- git: ~350kloc
- fish: ~50kloc
- ag: ~4kloc
- v8: ~520kloc
- node: ~28kloc
- scala: ~170kloc
Here's a hypothetical list of ways I could "trade down":
- OpenBSD: 11.5 million lines of code (this is for the whole system except X windows)
- "raw" WebKit: 1.8 million lines of code
- mesa: a million lines of code
- vis: 25kloc (a vim-like editor: "the goal could be summarized as 80% of vim's features implemented in roughly 1% of the code")
- mercurial: 110kloc
- btrfs: 86kloc
- weston: 30kloc
- dash: 14kloc
- pacman: 20kloc
- grep: 2kloc
- st: 4kloc (a replacement terminal emulator. for comparison, xterm is around 90kloc)
note: some of the older C programs seem to also implement their own malloc and realloc.
Where are the hotspots in this profile?
- The kernel & the web browser are both on the order of 10^7
- the graphics system and programming vm => 10^6
- editing and version controlling files => 10^5
- the filesystem and window compositor => 10^4
- the programming language, shell, and package manager => a smaller 10^4
- fast file search, terminal emulator => 10^3
Here’s the thing: I don’t think editing and version controlling files should be in that 10^5 tier. What’s a reasonable lower bound for the complexity of these tasks?
The first self-host of git was written in four days - 853 lines of C, back in the 10^3 range. And as far as text editing is concerned, the simplest C text editor that I know of is kilo, antirez's toy editor: 1148 lines of C. Let's slot these in as lower bounds. What does our profile look like now?
- The kernel and web browser => 10^7
- the graphics system and programming vm => 10^6
- the filesystem, window compositor, shell and programming language => 10^5
- search, terminal emulator, fuzzy selecting, editing, and version controlling text => 10^3
In the case of TinyCC and Duktape, their bigger sibling language implementations are at least an order of magnitude bigger (Clang is 680k, jsc-v8 are between 250 and 500k). Do optimizations of a language necessitate an order of magnitude increase in codebase size?
A project that's exploring this is qbe - it aims to provide "70% of the performance of advanced compilers [ed: think LLVM!] in 10% of the code" - currently it's 10kloc. The folks from the suckless project are working on a C frontend for this called scc, which is a work in progress, but is currently 12kloc.
So let's try and split these programs up into categories. Where is most of our complexity budget spent? Does the distribution make sense to us?
- programmer interface:
- dash: 14kloc (C)
- pick: 1kloc (C)
- ag: 4kloc (C)
- find: 2kloc (C)
- git: 1kloc (C)
- kilo: 2kloc (C)
- programming system:
- tinycc: 61kloc (C)
- make: 12kloc
- user interface:
- st: 4kloc (C)
- mesa: 1 million (C)
- webkit: 2 million (C++)
Anyway, moving on to the graphics stack:
There are two bigger monsters underlying the graphics stack: the drivers for a particular graphics architecture (Intel's, for the sake of the conversation, as it's fully open source), and Mesa, the linux graphics API.
The Intel graphics codebase contains support for many different wholly separate codepaths for each graphics card. It would be interesting to try and see the graph of dependencies within the driver to find out how big the codepath actually used by any one particular driver is; I have a hunch that this would drop the codebase to a surmountable size that I could actually comprehend.
I have a hunch that a similar trick could be played with the Mesa codebase, but haven't done the investigative work required to verify.
Maybe we're getting into tenable territory? Sans graphics and the web, we're at a somewhat manageable 100,000 lines of code, not counting tests or docs for those codebases that have them (eek). Graphics has seen many interesting experiments (check out nile, from Alan Kay's lab, tinygl, and the tinyrenderer course), and Servo, Mozilla's research browser project, is the first fresh implementation of the Web platform in 20 years (both Webkit and Blink came from khtml, which was forked from the even earlier khtmlw in 1998), and is an order of magnitude smaller than Webkit so far.
I see a lot of promise here. There's stranger complications (how are we going to comprehend the web?) but perhaps this is a good place to stop and think.
Thanks to Julia, Panashe, and Dan for their feedback on this post.