feat(web/tvl/blog): Write Tvix introduction blog post

This post is intended to just let people know about the existence of
Tvix, tell them a bit about the background and how to follow along.

Change-Id: Ib5194d3aa385a0e30b4768ba28cb063784f6e0a3

web/tvl/blog/default.nix

@@ -9,10 +9,10 @@
 
   posts = [
     {
-      key = "kicking-off-tvix";
+      key = "rewriting-nix";
-      title = "Kicking off Tvix";
+      title = "Tvix: We are rewriting Nix";
       date = 1636038556;
-      content = ./kicking-off-tvix.md;
+      content = ./rewriting-nix.md;
       draft = true;
     }
   ];

web/tvl/blog/kicking-off-tvix.md

@@ -1 +0,0 @@
-To be written.

web/tvl/blog/rewriting-nix.md

@@ -0,0 +1,79 @@
+Evaluating the Nix programming language, used by the Nix package
+manager, is currently very slow. This becomes apparent in all projects
+written in Nix that are not just simple package definitions, for
+example:
+
+* the NixOS module system
+* TVL projects like
+  [`//nix/yants`](https://at.tvl.fyi/?q=%2F%2Fnix%2Fyants) and
+  [`//web/bubblegum`](https://at.tvl.fyi/?q=%2F%2Fweb%2Fbubblegum).
+* the code that [generates build
+  instructions](https://at.tvl.fyi/?q=%2F%2Fops%2Fpipelines) for TVL's
+  [CI setup](https://tvl.fyi/builds)
+
+Whichever project you pick, they all suffer from issues with the
+language implementation. At TVL, it takes us close to a minute to
+create the CI instructions for our monorepo at the moment - despite it
+being a plain Nix evaluation. Running our Nix-native build systems for
+[Go](https://code.tvl.fyi/about/nix/buildGo) and [Common
+Lisp](https://code.tvl.fyi/about/nix/buildLisp) takes much more time
+than we would like.
+
+Some time last year a few of us got together and started investigating
+ways to modernise the current architecture of Nix and figure out how
+to improve the speed of some of the components. We created over [250
+commits](https://cl.tvl.fyi/q/topic:tvix) in our fork of the Nix 2.3
+codebase at the time, tried [performance
+experiments](https://cl.tvl.fyi/c/depot/+/1123/) aimed at improving
+the current evaluator and fought [gnarly
+bugs](https://cl.tvl.fyi/c/depot/+/1504).
+
+After a while we realised that we are treading water: Some of our
+ideas are too architecturally divergent from Nix to be done on top of
+the existing codebase, and the memory model of Nix causes significant
+headaches when trying to do any kind of larger change.
+
+We needed an alternative approach and started brainstorming on a bent
+whiteboard in a small flat in Hurghada, Egypt.
+
+![flokli & tazjin brainstorming](https://static.tvl.fyi/latest/flokli_tazjin_tvix.webp)
+
+<!-- TODO(tazjin): Wait for adisbladis approval to use this picture
+![adisbladis & tazjin brainstorming](https://static.tvl.fyi/latest/adisbladis_tazjin_tvix.webp)
+-->
+
+Half a year later we are now ready to announce our new project:
+**Tvix**, a re-imagined Nix with full nixpkgs compatibility. Tvix is
+generously funded [by NLNet](https://nlnet.nl/project/Tvix/) (thanks!)
+and we are ready to start implementing it.
+
+The [Tvix
+architecture](https://code.tvl.fyi/about/tvix/docs/components.md) is
+designed to be modular: It should be possible to write an evaluator
+that plugs in the Guix language, to use arbitrary builders, and to
+replace the store implementation.
+
+Tvix has these high-level goals:
+
+* Creating an alternative implementation of Nix that is **fully
+  compatible with nixpkgs**, as we believe that most of the value of
+  Nix currently lives in the massive amount of community contributions
+  to nixpkgs.
+* A new Nix language implementation with a more efficient interpreter,
+  and without the strict separation between evaluation and build
+  phases
+* Well-defined interaction protocols for how the three different
+  components (evaluator, builder, store) interact.
+* A builder implementation using OCI instead of custom sandboxing
+  code.
+
+Tvix is not intended to *replace* Nix, instead we want to improve the
+ecosystem by offering a diversity of implementations. However, we do
+not intend to support experimental features.
+
+As things ramp up we will be posting more information on this blog,
+for now you can keep an eye on
+[`//tvix`](https://cs.tvl.fyi/depot/-/tree/tvix) in the TVL monorepo,
+subscribe to [our feed](https://tvl.fyi/feed.atom).
+
+Stay tuned!