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diff --git a/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main--chapters.vtt b/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main--chapters.vtt new file mode 100644 index 00000000..ef14c4ae --- /dev/null +++ b/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main--chapters.vtt @@ -0,0 +1,92 @@ +WEBVTT + + +00:00:00.000 --> 00:00:17.081 +Rune + +00:00:17.082 --> 00:00:57.167 +The Emacs core + +00:00:57.168 --> 00:01:55.864 +Why create this? + +00:01:55.865 --> 00:03:01.314 +How does this compare to other projects? + +00:03:01.315 --> 00:03:32.440 +Multi-threading + +00:03:32.441 --> 00:03:47.647 +Multi-threading elisp + +00:03:47.648 --> 00:04:32.637 +No-GIL method + +00:04:32.638 --> 00:04:51.251 +Actors + +00:04:51.252 --> 00:05:34.679 +Multi-threading elisp (functions) + +00:05:34.680 --> 00:05:57.089 +Caveats + +00:05:57.090 --> 00:06:38.248 +Multi-threading elisp (data) + +00:06:38.249 --> 00:06:57.883 +Copy values to other threads on demands + +00:06:57.884 --> 00:08:11.902 +Multi-threading elisp (buffers) + +00:08:11.903 --> 00:08:46.918 +Would this actually be useful? + +00:08:46.919 --> 00:09:16.536 +Precise garbage collection + +00:09:16.537 --> 00:10:38.712 +How Emacs used to deal with roots + +00:10:38.713 --> 00:11:00.156 +Conservative stack scanning + +00:11:00.157 --> 00:12:38.828 +Movable objects + +00:12:38.829 --> 00:14:13.226 +How Rust makes precise GC easy + +00:14:13.227 --> 00:15:14.559 +Other Rust niceties: proc macro + +00:15:14.560 --> 00:16:01.040 +sum types + +00:16:01.041 --> 00:16:16.051 +Regex + +00:16:16.052 --> 00:16:27.209 +Parsers + +00:16:27.210 --> 00:16:58.918 +Other changes: GUI first, terminal second + +00:16:58.919 --> 00:17:16.304 +Off-screen cursor + +00:17:16.305 --> 00:17:24.439 +Image flow + +00:17:24.440 --> 00:18:36.344 +Testing + +00:18:36.345 --> 00:19:07.246 +Status + +00:19:07.247 --> 00:19:22.738 +Next directions + +00:19:22.739 --> 00:20:06.000 +How to get involved diff --git a/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main.vtt b/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main.vtt new file mode 100644 index 00000000..05826fb8 --- /dev/null +++ b/2024/captions/emacsconf-2024-rust--an-experimental-emacs-core-in-rust--troy-hinckley--main.vtt @@ -0,0 +1,1351 @@ +WEBVTT captioned by sachac, checked by bhavin + +NOTE Rune + +00:00:00.000 --> 00:00:05.119 +Hello, EmacsConf. My name is Troy Hinckley, and this is my + +00:00:05.120 --> 00:00:08.759 +talk on Rune, a Rust implementation in Emacs. We strive to be + +00:00:08.760 --> 00:00:11.839 +bug compatible with Emacs, so you can use the same Elisp. + +00:00:11.840 --> 00:00:14.879 +It's still a fairly early stage experimental project, and + +00:00:14.880 --> 00:00:17.081 +we have some basic things implemented. + +NOTE The Emacs core + +00:00:17.082 --> 00:00:19.946 +Before I get started, I want to talk a bit more + +00:00:19.947 --> 00:00:21.847 +about what the core is. + +00:00:21.848 --> 00:00:24.559 +So the Emacs core, it includes the runtime, the interpreter, + +00:00:24.560 --> 00:00:26.439 +garbage collector, everything used to run the code. + +00:00:26.440 --> 00:00:29.799 +It includes the GUI. It includes all the data structures. + +00:00:29.800 --> 00:00:31.919 +If you look underneath all the Elisp data structures, + +00:00:31.920 --> 00:00:33.599 +there's C code underneath there, + +00:00:33.600 --> 00:00:35.559 +as well as the auxiliary functions + +00:00:35.560 --> 00:00:39.239 +of which there's about 1500. In making this talk, I don't + +00:00:39.240 --> 00:00:40.919 +want to give the impression that I'm saying the core is + +00:00:40.920 --> 00:00:42.879 +outdated or that needs to be replaced or that it can't be + +00:00:42.880 --> 00:00:45.519 +evolved on its own, because clearly it has continued to + +00:00:45.520 --> 00:00:48.319 +evolve. If we look in just the last few years, we can see that + +00:00:48.320 --> 00:00:50.439 +we've added native compilation, we've added tree-sitter + +00:00:50.440 --> 00:00:52.759 +support, we've added color emoji, and there's work right + +00:00:52.760 --> 00:00:57.167 +now to add a new garbage collector to Emacs as well. + +NOTE Why create this? + +00:00:57.168 --> 00:01:01.071 +Why create this project? Emacs has a long history. + +00:01:01.072 --> 00:01:04.535 +It has a lot of users. It needs to support a big community. + +00:01:04.536 --> 00:01:06.837 +Because of that, it has to be very conservative + +00:01:06.838 --> 00:01:10.321 +about what things it can allow into the project. + +00:01:10.322 --> 00:01:11.639 +Forks like this create an + +00:01:11.640 --> 00:01:15.586 +opportunity to experiment and try new approaches. + +00:01:15.587 --> 00:01:18.799 +This is particularly a good use case for Rust because the C core, + +00:01:18.800 --> 00:01:20.849 +it's pretty well tested. It's been around for a long time. + +00:01:20.850 --> 00:01:22.959 +A lot of the bugs have been ironed out, but when you're doing a + +00:01:22.960 --> 00:01:26.439 +new greenfield project, it's very easy to introduce new + +00:01:26.440 --> 00:01:28.774 +undefined behavior and memory unsafety + +00:01:28.775 --> 00:01:32.376 +and stuff like that. Rust protects us from most of that, + +00:01:32.377 --> 00:01:34.937 +but it also gives us the ability to be fast + +00:01:34.938 --> 00:01:37.883 +and has a strong ecosystem behind it. + +00:01:37.884 --> 00:01:40.399 +Rust is also really good at multi-threading. + +00:01:40.400 --> 00:01:43.399 +Their phrase in the community is fearless concurrency. + +00:01:43.400 --> 00:01:45.559 +They should be able to write concurrent programs without + +00:01:45.560 --> 00:01:49.319 +having to worry about data races. It's also really high + +00:01:49.320 --> 00:01:51.839 +performance. It has a really good regex engine. It's known + +00:01:51.840 --> 00:01:55.864 +for its non-copy I/O as well. + +NOTE How does this compare to other projects? + +00:01:55.865 --> 00:01:57.479 +How does this compare to other + +00:01:57.480 --> 00:01:59.919 +Rust and Emacs projects, whether there's been a couple? The + +00:01:59.920 --> 00:02:02.799 +first is Remacs. This project was the first. It took an + +00:02:02.800 --> 00:02:05.519 +outside-in approach. Basically you could take a C + +00:02:05.520 --> 00:02:09.319 +function and replace it with a Rust function and build it + +00:02:09.320 --> 00:02:11.799 +together as one executable. This is pretty easy to do + +00:02:11.800 --> 00:02:14.639 +because they could both talk over the C ABI. You could + +00:02:14.640 --> 00:02:16.479 +swap out functions once at a time. They made really good + +00:02:16.480 --> 00:02:20.279 +progress at first, but eventually they ran into the problem + +00:02:20.280 --> 00:02:23.079 +that as you get down to the really core parts of it, you can't + +00:02:23.080 --> 00:02:25.919 +just replace one function at a time anymore, because some of + +00:02:25.920 --> 00:02:28.159 +that functionality is connected to other things. Like for + +00:02:28.160 --> 00:02:30.359 +example, you can't replace the garbage collector without + +00:02:30.360 --> 00:02:32.759 +replacing the entire garbage collection system. So the + +00:02:32.760 --> 00:02:36.279 +progress really kind of slowed down. Another issue with it + +00:02:36.280 --> 00:02:38.839 +was, is that they were doing a one-to-one rewrite, so they + +00:02:38.840 --> 00:02:41.079 +weren't adding any new features or functionality, just + +00:02:41.080 --> 00:02:43.879 +taking the same code and replacing it in Rust, which doesn't + +00:02:43.880 --> 00:02:46.801 +add any advantages in and of itself. + +00:02:46.802 --> 00:02:50.399 +This spawned Emacs-NG, which was kind of the spiritual successor to + +00:02:50.400 --> 00:02:52.746 +Remacs, where they decided to add new functionality, + +00:02:52.747 --> 00:02:55.808 +the biggest one being a JavaScript runtime, + +00:02:55.809 --> 00:02:58.230 +as well as some new renderers to Emacs. + +00:02:58.231 --> 00:03:01.314 +This is no longer actively developed though. + +NOTE Multi-threading + +00:03:01.315 --> 00:03:04.079 +In this project, one of the big focuses we have is + +00:03:04.080 --> 00:03:07.559 +on multi-threading. The C core itself is, everything is + +00:03:07.560 --> 00:03:09.959 +designed around being single-threaded, all the data + +00:03:09.960 --> 00:03:13.039 +structures and everything like that. Rust has a great + +00:03:13.040 --> 00:03:15.719 +concurrency story. In Rust, everything is intended to be + +00:03:15.720 --> 00:03:18.199 +multi-threaded. That doesn't mean that everything has to + +00:03:18.200 --> 00:03:20.719 +run on multiple threads, but you can't write something that + +00:03:20.720 --> 00:03:22.719 +is limited to only running in a single-threaded + +00:03:22.720 --> 00:03:25.799 +environment. So this makes it really easy to use all the + +00:03:25.800 --> 00:03:28.039 +existing packages and build something that is + +00:03:28.040 --> 00:03:30.480 +concurrency safe. which is what we've done here, + +00:03:30.481 --> 00:03:32.440 +and that was relatively easy to do. + +NOTE Multi-threading elisp + +00:03:32.441 --> 00:03:34.781 +But adding it to Elisp is the hard part, + +00:03:34.782 --> 00:03:36.502 +because we've got to come up with a good model + +00:03:36.503 --> 00:03:39.624 +for Lisp, and Elisp is just a giant ball + +00:03:39.625 --> 00:03:41.479 +of mutable state. We need to find some + +00:03:41.480 --> 00:03:44.566 +way to tame that so we can make workable concurrency + +00:03:44.567 --> 00:03:47.647 +out of it. There's really two ways you can do this. + +NOTE No-GIL method + +00:03:47.648 --> 00:03:49.268 +One is what I call the no-GIL method. + +00:03:49.269 --> 00:03:51.399 +This is what Python is doing, where + +00:03:51.400 --> 00:03:53.919 +you take all of your data structures, you make them + +00:03:53.920 --> 00:03:56.439 +concurrency safe, and then you just leave it up to the + +00:03:56.440 --> 00:03:58.119 +programmer to decide what they're going to do with it. + +00:03:58.120 --> 00:04:00.467 +They've got to build safe abstractions on top of that. + +00:04:00.468 --> 00:04:03.086 +One of the big downsides with this is that + +00:04:03.087 --> 00:04:05.247 +it comes with a pretty high cost. + +00:04:05.248 --> 00:04:07.799 +The last benchmarks I've seen is that by making + +00:04:07.800 --> 00:04:10.879 +everything concurrency safe in Python, single-threaded + +00:04:10.880 --> 00:04:15.799 +code is about 20% slower in some benchmarks. + +00:04:15.800 --> 00:04:19.079 +Since most code is single-threaded, this has a big + +00:04:19.080 --> 00:04:21.039 +performance impact for most code that isn't taking + +00:04:21.040 --> 00:04:23.719 +advantage of the multi-threading. The other thing is this + +00:04:23.720 --> 00:04:26.279 +introduces a lot of nasty concurrency bugs because you can + +00:04:26.280 --> 00:04:29.039 +have anything mutating any part of the data from any thread, + +00:04:29.040 --> 00:04:32.637 +even if you can't have memory unsafety per se. + +NOTE Actors + +00:04:32.638 --> 00:04:34.738 +The other option is actors, + +00:04:34.739 --> 00:04:36.639 +which are a really known way to approach this, + +00:04:36.640 --> 00:04:39.079 +where you trade some of that flexibility that you get + +00:04:39.080 --> 00:04:43.719 +with fully concurrent for more control and. Code and + +00:04:43.720 --> 00:04:45.839 +functions are shared between all the different threads, + +00:04:45.840 --> 00:04:50.599 +but data has to be passed along channels between different + +00:04:50.600 --> 00:04:51.251 +actors. + +NOTE Multi-threading elisp (functions) + +00:04:51.252 --> 00:04:52.919 +We want the functions to be shared, and this + +00:04:52.920 --> 00:04:55.159 +should be pretty easy because we don't mutate functions + +00:04:55.160 --> 00:05:00.119 +like we do data, except when we do. In Lisp, functions are + +00:05:00.120 --> 00:05:03.239 +just lists like anything else. So you can mutate them + +00:05:03.240 --> 00:05:06.279 +just like lists. Even if you're not talking about + +00:05:06.280 --> 00:05:09.159 +interpreted code, like if you have a native compiled + +00:05:09.160 --> 00:05:11.959 +function, you can still mutate the constants inside the + +00:05:11.960 --> 00:05:14.839 +function. For example, here we have a function returns a + +00:05:14.840 --> 00:05:17.679 +string. We take that string out, we mutate that string, and + +00:05:17.680 --> 00:05:23.079 +now the function returns a different string. In Rune, we + +00:05:23.080 --> 00:05:24.999 +enforce that all functions, their constants are + +00:05:25.000 --> 00:05:27.199 +immutable. You can't mutate the insides of a function. You + +00:05:27.200 --> 00:05:29.239 +can still swap out functions and redefine them, but you + +00:05:29.240 --> 00:05:32.239 +can't mutate the inside of a function. This enables them + +00:05:32.240 --> 00:05:34.679 +to be safely shared across threads. + +NOTE Caveats + +00:05:34.680 --> 00:05:36.400 +However, there are some caveats to this. + +00:05:36.401 --> 00:05:38.159 +For example, some functions actually do + +00:05:38.160 --> 00:05:41.439 +need to mutate their own data. The example that we run into is + +00:05:41.440 --> 00:05:44.839 +cl-generic. It uses a method cache. So it has to be able to + +00:05:44.840 --> 00:05:47.639 +update that cache. In this case, we just made a special + +00:05:47.640 --> 00:05:50.799 +case for this particular situation, but we don't know what + +00:05:50.800 --> 00:05:53.159 +more of these we're gonna run into the future where this is + +00:05:53.160 --> 00:05:57.089 +needed behavior to be able to mutate a function. + +NOTE Multi-threading elisp (data) + +00:05:57.090 --> 00:05:59.810 +Okay, so functions are pretty easy. + +00:05:59.811 --> 00:06:00.919 +They just can be shared between + +00:06:00.920 --> 00:06:05.159 +threads, but data can't be immutable, at least not into the + +00:06:05.160 --> 00:06:08.759 +model that Emacs currently has. We have two different + +00:06:08.760 --> 00:06:12.039 +ways to handle this. One is we require whenever you're + +00:06:12.040 --> 00:06:14.399 +calling some other code in a different thread, you have to + +00:06:14.400 --> 00:06:17.039 +send all the variables that it's going to need over to that + +00:06:17.040 --> 00:06:19.159 +thread. This is how you traditionally do inside actors. + +00:06:19.160 --> 00:06:21.919 +Any data that needs to go to a different actor needs to be sent + +00:06:21.920 --> 00:06:25.519 +over a channel. It's relatively easy implementation, but + +00:06:25.520 --> 00:06:28.159 +this is difficult in the Emacs case because everything is + +00:06:28.160 --> 00:06:30.799 +going to be accessing different variables. That means + +00:06:30.800 --> 00:06:33.119 +when you call something, you have to know ahead of time, all + +00:06:33.120 --> 00:06:34.879 +the different variables that are gonna be accessed inside + +00:06:34.880 --> 00:06:38.248 +that other thread and put those in when you call it. + +NOTE Copy values to other threads on demands + +00:06:38.249 --> 00:06:40.959 +The other option we're using is we're copying values to the + +00:06:40.960 --> 00:06:43.439 +other threads on demand. If you're running a thread, it + +00:06:43.440 --> 00:06:45.759 +tries to look up a variable. It doesn't have any value for + +00:06:45.760 --> 00:06:48.759 +that variable. It will go back and ask the main thread and it + +00:06:48.760 --> 00:06:50.959 +will copy that value into that thread and it can continue + +00:06:50.960 --> 00:06:53.399 +execution. This is nice because you can just launch some + +00:06:53.400 --> 00:06:55.639 +code and it'll take care of handling all the data transfer + +00:06:55.640 --> 00:06:57.883 +for you. + +NOTE Multi-threading elisp (buffers) + +00:06:57.884 --> 00:07:00.359 +But we don't want to be copying around is buffers, + +00:07:00.360 --> 00:07:04.199 +because they can be really large. In this case, we have a + +00:07:04.200 --> 00:07:07.599 +mutex. Each thread could only have one current buffer that + +00:07:07.600 --> 00:07:12.279 +it has an exclusive lock to. This comes with some + +00:07:12.280 --> 00:07:16.079 +trade-offs, big one being that if the user tries to access + +00:07:16.080 --> 00:07:18.359 +some buffer, they want to type something, and a background + +00:07:18.360 --> 00:07:20.239 +thread is holding onto that buffer, what do we do in that + +00:07:20.240 --> 00:07:24.959 +situation? And we still need to hold an exclusive lock, even + +00:07:24.960 --> 00:07:26.359 +if we're only going to read a buffer. If you have multiple + +00:07:26.360 --> 00:07:29.159 +readers, they each still need to take turns because we can't + +00:07:29.160 --> 00:07:30.999 +determine if at some point a thread is going to try and mutate + +00:07:31.000 --> 00:07:33.879 +the buffer. It has to be an exclusive lock. The other issue + +00:07:33.880 --> 00:07:37.799 +is buffer-locals. This is less of a implementation issue + +00:07:37.800 --> 00:07:40.519 +as much as it is a technical issue. Because you think about + +00:07:40.520 --> 00:07:42.759 +when we switch to a buffer, it has some buffer-local data and + +00:07:42.760 --> 00:07:45.399 +we have some thread-local data. As we go through, we're + +00:07:45.400 --> 00:07:47.599 +mutating everything. Those can get intertwined and + +00:07:47.600 --> 00:07:49.719 +pointing to each other. Then we switch away from that + +00:07:49.720 --> 00:07:51.679 +buffer. We need some quick way to be able to separate those + +00:07:51.680 --> 00:07:54.279 +out. The buffer-locals can go with the buffer-locals and + +00:07:54.280 --> 00:07:56.439 +the thread data can stay with thread data and make copies of + +00:07:56.440 --> 00:07:58.719 +anything that was pointing to the other side. But we don't + +00:07:58.720 --> 00:08:02.839 +have a good method to determine how to separate those two, + +00:08:02.840 --> 00:08:05.359 +like what data belongs to this and what data belongs to this, + +00:08:05.360 --> 00:08:08.199 +so that we can do that quickly. We haven't found a good + +00:08:08.200 --> 00:08:09.599 +solution to that yet, but it's something we're still + +00:08:09.600 --> 00:08:11.902 +working on. + +NOTE Would this actually be useful? + +00:08:11.903 --> 00:08:13.079 +The question is, would this actually be + +00:08:13.080 --> 00:08:15.959 +useful for doing real work inside Emacs? I would say, + +00:08:15.960 --> 00:08:17.959 +yes, there's a lot of things you can do with this. You could + +00:08:17.960 --> 00:08:20.239 +handle process output in the background. You can do syntax + +00:08:20.240 --> 00:08:23.479 +highlighting. You can do buffer search in parallel. You can + +00:08:23.480 --> 00:08:26.679 +do LSP. You can do fetching your mail in the background. You + +00:08:26.680 --> 00:08:29.639 +can have a window manager that doesn't block your window + +00:08:29.640 --> 00:08:32.319 +manager when Emacs is blocked. You could do + +00:08:32.320 --> 00:08:34.479 +something like a file system watcher that keeps up on files + +00:08:34.480 --> 00:08:37.559 +without blocking Emacs. This wouldn't be so great for + +00:08:37.560 --> 00:08:39.159 +building concurrent data structures or operating on + +00:08:39.160 --> 00:08:42.199 +shared data or building your own abstractions, because of the + +00:08:42.200 --> 00:08:46.039 +trade-offs that we've made here. Okay. That's talking + +00:08:46.040 --> 00:08:46.918 +about multi-threading. + +NOTE Precise garbage collection + +00:08:46.919 --> 00:08:47.599 +The other thing we're going to talk + +00:08:47.600 --> 00:08:51.319 +about is precise garbage collection. In Rune, we have a + +00:08:51.320 --> 00:08:54.439 +safe, precise garbage collection because of the Rust type + +00:08:54.440 --> 00:08:58.119 +system. Let's look at what the problem is with garbage + +00:08:58.120 --> 00:09:00.479 +collection in the first place. Really, the tricky part + +00:09:00.480 --> 00:09:03.719 +about garbage collection is rooting. How do we find out what + +00:09:03.720 --> 00:09:06.159 +the roots are? These are all the values that are on the + +00:09:06.160 --> 00:09:08.679 +stack or inside the registers. In this example here, we + +00:09:08.680 --> 00:09:11.919 +allocate an object. We call garbage_collect, that object's + +00:09:11.920 --> 00:09:13.536 +collected, and then we try and return it. + +00:09:13.537 --> 00:09:16.536 +It's no longer valid. + +NOTE How Emacs used to deal with roots + +00:09:16.537 --> 00:09:19.039 +Let's look at how Emacs used to deal with this + +00:09:19.040 --> 00:09:22.559 +problem way back in the day. There was a system called gcpro + +00:09:22.560 --> 00:09:26.319 +or GC Protect, which is basically designed that every time a + +00:09:26.320 --> 00:09:28.919 +value needed to survive past a garbage collection point, + +00:09:28.920 --> 00:09:32.359 +you had to try and protect it. In order to do this, you had + +00:09:32.360 --> 00:09:35.439 +to declare a struct, you had to put a macro around it to root + +00:09:35.440 --> 00:09:37.999 +the object, and then you had to unroot it when you were done-- + +00:09:38.000 --> 00:09:41.559 +past the garbage collection. Now the value is safe. You + +00:09:41.560 --> 00:09:44.039 +can see down here, I pulled these eight rules out from a + +00:09:44.040 --> 00:09:46.919 +really old version of the Emacs manual about all the things + +00:09:46.920 --> 00:09:49.279 +you had to keep track of when you were trying to use this + +00:09:49.280 --> 00:09:52.319 +system. All right, so there was a special handling for + +00:09:52.320 --> 00:09:54.639 +nested GC protects. You had to make sure the memory was + +00:09:54.640 --> 00:09:58.239 +initialized. You had to make sure that traps couldn't occur + +00:09:58.240 --> 00:10:00.839 +between allocating and when GC protect would happen. It + +00:10:00.840 --> 00:10:03.319 +can be tricky because you don't always know when a function + +00:10:03.320 --> 00:10:06.879 +that's getting called could potentially call garbage + +00:10:06.880 --> 00:10:10.719 +collection. So if you got something wrong, you also + +00:10:10.720 --> 00:10:12.719 +might not catch it for a long time because garbage + +00:10:12.720 --> 00:10:15.719 +collection may only get called one out of 99 times. The other + +00:10:15.720 --> 00:10:18.999 +99 times is just fine. That one time it happens and you + +00:10:19.000 --> 00:10:22.559 +can't reproduce the issue. When you do get this wrong and + +00:10:22.560 --> 00:10:24.439 +some, something doesn't get rooted and it gets + +00:10:24.440 --> 00:10:26.319 +overwritten, it generally doesn't show up right where the + +00:10:26.320 --> 00:10:28.799 +problem is. It gets showed up way later when you actually try + +00:10:28.800 --> 00:10:31.479 +and access the value and the value is invalid. You've got + +00:10:31.480 --> 00:10:33.639 +to track it back to where that thing did not get properly + +00:10:33.640 --> 00:10:37.359 +rooted. It's a huge source of bugs and very hard to + +00:10:37.360 --> 00:10:38.712 +maintain. + +NOTE Conservative stack scanning + +00:10:38.713 --> 00:10:40.119 +Emacs decided to go with a different path, + +00:10:40.120 --> 00:10:42.399 +which we call conservative stack scanning. Basically, + +00:10:42.400 --> 00:10:45.239 +the garbage collector just looks at the stack and all the + +00:10:45.240 --> 00:10:47.959 +registers and any data inside there that looks like it could + +00:10:47.960 --> 00:10:52.279 +be a pointer, it treats it as a pointer. This is nice because + +00:10:52.280 --> 00:10:54.711 +you get really easy root tracking, + +00:10:54.712 --> 00:10:56.113 +but it also comes with some trade-offs, + +00:10:56.114 --> 00:11:00.156 +mostly that your objects are no longer movable. + +NOTE Movable objects + +00:11:00.157 --> 00:11:03.079 +Why would we want movable objects in Emacs? + +00:11:03.080 --> 00:11:05.839 +There's a couple of different reasons. One is compaction. + +00:11:05.840 --> 00:11:08.199 +You can take all your heap, you can pack that on down because + +00:11:08.200 --> 00:11:11.239 +you can coalesce all your objects together. Another is that + +00:11:11.240 --> 00:11:13.239 +it's easy to implement generational garbage collection. + +00:11:13.240 --> 00:11:16.039 +You can just copy everything out of your minor heap into your + +00:11:16.040 --> 00:11:21.839 +older heap. Really, Emacs is kind of uniquely ideal for + +00:11:21.840 --> 00:11:24.279 +generational collection, because the typical way we + +00:11:24.280 --> 00:11:27.799 +interact with Emacs is as a series of commands. You execute + +00:11:27.800 --> 00:11:29.959 +some command, you'd execute the next command, you execute + +00:11:29.960 --> 00:11:33.199 +a command. It could be happening every key press, it could be + +00:11:33.200 --> 00:11:36.759 +happening with M-x. However long that command is, that is + +00:11:36.760 --> 00:11:40.959 +the ideal length for the minor collection generation, the + +00:11:40.960 --> 00:11:43.399 +first generation. Because once you're done with that + +00:11:43.400 --> 00:11:45.879 +generation, anything that's still existing is going to be + +00:11:45.880 --> 00:11:49.079 +around for a very long time. So that works out really well + +00:11:49.080 --> 00:11:52.279 +for Emacs. We want to make this a generational collector. + +00:11:52.280 --> 00:11:56.199 +The other thing is with object layout. We use a lot of lists + +00:11:56.200 --> 00:12:00.559 +inside Emacs Lisp. Every time you go to the cdr, you've + +00:12:00.560 --> 00:12:03.039 +got to be chasing a pointer around the heap and following + +00:12:03.040 --> 00:12:05.439 +that. That can potentially result in cache misses and + +00:12:05.440 --> 00:12:08.239 +all sorts of other things like that. So it can take a long + +00:12:08.240 --> 00:12:12.159 +time. It can be quite slow. But if you have the ability to move + +00:12:12.160 --> 00:12:16.559 +objects, you can just relocate an entire list and lay it out + +00:12:16.560 --> 00:12:19.168 +in an array right next to each other inside memory. + +00:12:19.169 --> 00:12:22.479 +So iterating over it is just as fast as iterating over an array. + +00:12:22.480 --> 00:12:25.421 +But you can only do that if you have movable objects. + +00:12:25.422 --> 00:12:28.399 +I'll point out here too, that with conservative stack scanning, + +00:12:28.400 --> 00:12:31.599 +it's not that all objects are immovable. It's only ones that + +00:12:31.600 --> 00:12:35.519 +are pointed to from the stack or from the registers that have + +00:12:35.520 --> 00:12:38.828 +to become immovable. + +NOTE How Rust makes precise GC easy + +00:12:38.829 --> 00:12:41.039 +Let's look at how Rust makes precise + +00:12:41.040 --> 00:12:44.439 +garbage collection easy. Here I have some Rust code to + +00:12:44.440 --> 00:12:47.279 +show kind of how the lifetime system works and what we call + +00:12:47.280 --> 00:12:49.879 +XOR mutability, where we can only have one mutable + +00:12:49.880 --> 00:12:52.879 +reference or multiple immutable references to the same + +00:12:52.880 --> 00:12:56.199 +thing. Here we declare a vector, we take a reference to the + +00:12:56.200 --> 00:12:59.199 +first element of the vector, and then we mutate the vector. + +00:12:59.200 --> 00:13:02.239 +Now this could potentially resize the vector and move it to a + +00:13:02.240 --> 00:13:04.919 +different location in memory, so that reference is no + +00:13:04.920 --> 00:13:07.759 +longer valid. The nice thing is, Rust catches this for + +00:13:07.760 --> 00:13:10.479 +us. It says, hey, this is no longer valid. This reference + +00:13:10.480 --> 00:13:14.519 +can't survive past when you mutated it. Okay? That's + +00:13:14.520 --> 00:13:17.559 +exactly what we want for a garbage collector. You can see + +00:13:17.560 --> 00:13:19.879 +here, we take this in a garbage collection context, we + +00:13:19.880 --> 00:13:23.359 +create a new context object, we add an object, we call + +00:13:23.360 --> 00:13:26.759 +garbage_collect, then we try and access that object. It's no + +00:13:26.760 --> 00:13:29.199 +longer accessible, and Rust will prevent us from trying to + +00:13:29.200 --> 00:13:34.839 +access that variable. So, how do we solve this? We have a + +00:13:34.840 --> 00:13:39.759 +root macro. We declared this root macro, it lets us take the + +00:13:39.760 --> 00:13:41.759 +object and let it live past garbage collection, and + +00:13:41.760 --> 00:13:45.319 +everything works out. The nice thing is, this root macro + +00:13:45.320 --> 00:13:47.799 +will get dropped when it's out of scope, so we don't have to + +00:13:47.800 --> 00:13:51.519 +worry about the un-gc-protect step of this. Statically, + +00:13:51.520 --> 00:13:55.799 +Rust will verify and tell us any object that needs to be + +00:13:55.800 --> 00:13:58.279 +rooted. If we try and access it, it'll tell us it's invalid. + +00:13:58.280 --> 00:14:00.999 +We have this root macro and then we can access it. So in + +00:14:01.000 --> 00:14:03.759 +that way, we have safe, precise garbage collection without + +00:14:03.760 --> 00:14:07.479 +any chance of introducing undefined behavior, which is + +00:14:07.480 --> 00:14:09.999 +really, really powerful. It's really easy because the + +00:14:10.000 --> 00:14:13.226 +type system will catch it all for us. + +NOTE Other Rust niceties: proc macro + +00:14:13.227 --> 00:14:15.147 +There's some other Rust niceties I want to kind of + +00:14:15.148 --> 00:14:16.799 +talk through that are useful, but + +00:14:16.800 --> 00:14:21.079 +are not, you know, star features. One is proc macros. You + +00:14:21.080 --> 00:14:23.679 +can see up on the top, you can see how you declare a function + +00:14:23.680 --> 00:14:27.359 +inside the C core. All right. You have to use the macro. You + +00:14:27.360 --> 00:14:29.141 +have to put the list type, the function type, + +00:14:29.142 --> 00:14:30.963 +the struct type, the different types of arguments + +00:14:30.964 --> 00:14:33.225 +or different number of arguments, the doc string, + +00:14:33.226 --> 00:14:36.023 +and then you can put your argument listing down inside there. + +00:14:36.024 --> 00:14:37.984 +On the Rust side, we just write this like we would + +00:14:37.985 --> 00:14:40.044 +any other Rust function. And then we put + +00:14:40.045 --> 00:14:41.285 +the defun proc macro on there + +00:14:41.286 --> 00:14:44.186 +and it takes care of everything for us behind the scenes. + +00:14:44.187 --> 00:14:46.407 +A couple of cool additional things we can do with this + +00:14:46.408 --> 00:14:48.727 +is that we don't have to make everything just an object. + +00:14:48.728 --> 00:14:49.759 +We can actually make things + +00:14:49.760 --> 00:14:54.239 +more specific types. Here we have symbols. As well as + +00:14:54.240 --> 00:14:56.279 +you can see subfeature, it's an optional parameter, and we + +00:14:56.280 --> 00:15:00.919 +just make it an option inside Rust and it automatically make + +00:15:00.920 --> 00:15:03.599 +it an optional inside Elisp. + +00:15:03.600 --> 00:15:05.181 +This makes them really easy to write. + +00:15:05.182 --> 00:15:06.439 +I can't take credit for this is because this is + +00:15:06.440 --> 00:15:09.119 +something that I saw inside Remacs and I stole from them, but + +00:15:09.120 --> 00:15:11.439 +it makes the functions really easy to call from each other + +00:15:11.440 --> 00:15:14.559 +and really easy to write as well. + +NOTE sum types + +00:15:14.560 --> 00:15:18.523 +Another thing that's really nice is sum types. + +00:15:18.524 --> 00:15:21.039 +In the C core, if I wanted to get a + +00:15:21.040 --> 00:15:23.759 +string out of an object, I would first need to check that it's + +00:15:23.760 --> 00:15:28.319 +a string and then dereference it as a string. But if it's not a + +00:15:28.320 --> 00:15:30.679 +string, I may introduce undefined behavior. So in + +00:15:30.680 --> 00:15:32.799 +complicated code, I have to make sure that I have always + +00:15:32.800 --> 00:15:34.959 +checked what type it is before I try and dereference that + +00:15:34.960 --> 00:15:37.879 +type. We don't have to worry about any of that inside Rust + +00:15:37.880 --> 00:15:41.319 +because we can untag a value and we can use their some types, + +00:15:41.320 --> 00:15:44.399 +basically create an enum and we can match on what the + +00:15:44.400 --> 00:15:47.639 +different values can be. Then we only get out the types + +00:15:47.640 --> 00:15:50.359 +that are viable or are actually there. So we never + +00:15:50.360 --> 00:15:52.159 +accidentally get something out of an object that we didn't + +00:15:52.160 --> 00:15:54.239 +mean to, or dereference it as something that doesn't + +00:15:54.240 --> 00:15:56.879 +really exist. We can just match on it and we can get out the + +00:15:56.880 --> 00:16:01.040 +values that we need, which is really, really powerful. + +NOTE Regex + +00:16:01.041 --> 00:16:03.639 +So there's some other Rust niceties as well working with here. + +00:16:03.640 --> 00:16:07.799 +One is the regex engine inside Rust is really fast, high + +00:16:07.800 --> 00:16:10.959 +performance. We are using that for the Elixir regex + +00:16:10.960 --> 00:16:14.879 +engine to give it high performance and worst-case + +00:16:14.880 --> 00:16:16.051 +guarantees. + +NOTE Parsers + +00:16:16.052 --> 00:16:18.599 +The other is that Rust has a lot of really good + +00:16:18.600 --> 00:16:21.559 +parsers for things like JSON that are no copy parsers that + +00:16:21.560 --> 00:16:24.719 +are high performance. We can use those inside Rune as + +00:16:24.720 --> 00:16:27.209 +well. + +NOTE Other changes: GUI first, terminal second + +00:16:27.210 --> 00:16:29.439 +There's a handful of other changes we're working on + +00:16:29.440 --> 00:16:33.119 +that are not Rust-specific, but we'd like to see. The first is + +00:16:33.120 --> 00:16:36.759 +being GUI first, terminal second. This means two things. + +00:16:36.760 --> 00:16:40.039 +First is that we have all of our key bindings. Right now + +00:16:40.040 --> 00:16:43.279 +inside Emacs, C-i and TAB are bound to the same key + +00:16:43.280 --> 00:16:45.039 +binding by default, because that's how it works inside the + +00:16:45.040 --> 00:16:48.119 +terminal. In the GUI, you shouldn't have that limitation. + +00:16:48.120 --> 00:16:52.559 +The second is that the GUI should not block when Lisp is + +00:16:52.560 --> 00:16:55.199 +blocked. It should be independent of that. Your GUI can + +00:16:55.200 --> 00:16:58.918 +still continue to operate when Lisp is running. + +NOTE Off-screen cursor + +00:16:58.919 --> 00:17:01.279 +The other is the ability to have an off-screen cursor + +00:17:01.280 --> 00:17:02.699 +so that you can be typing on something, + +00:17:02.700 --> 00:17:04.319 +you can scroll up and down and the point + +00:17:04.320 --> 00:17:06.719 +doesn't have to follow you where you lose your place where + +00:17:06.720 --> 00:17:09.399 +you were before. You don't have to intentionally set a mark. + +00:17:09.400 --> 00:17:11.199 +You can just scroll and then start typing and it'll go back up + +00:17:11.200 --> 00:17:13.879 +to where it was before, like it works in most applications. + +00:17:13.880 --> 00:17:16.304 +And this can be optional. + +NOTE Image flow + +00:17:16.305 --> 00:17:18.079 +The other is image flow. We want it + +00:17:18.080 --> 00:17:20.879 +so that you can easily flow images and you can have large + +00:17:20.880 --> 00:17:23.159 +images and scroll past them without jumping and you can flow + +00:17:23.160 --> 00:17:24.439 +text around images. + +NOTE Testing + +00:17:24.440 --> 00:17:29.799 +How are we testing this project? Because there's a lot of + +00:17:29.800 --> 00:17:33.159 +things that you could get wrong here. One thing we're doing + +00:17:33.160 --> 00:17:38.039 +is we're using ERT. Emacs ships with over 7,000 built-in + +00:17:38.040 --> 00:17:42.879 +tests--Elisp tests. We are using this test suite to test + +00:17:42.880 --> 00:17:45.079 +our project as well. We can kind of use this as a dashboard + +00:17:45.080 --> 00:17:47.679 +of saying how close are we to getting to parity with GNU + +00:17:47.680 --> 00:17:52.319 +Emacs. The other thing that we have is a tool called elprop, + +00:17:52.320 --> 00:17:55.279 +which is an external utility that basically tests for + +00:17:55.280 --> 00:17:58.719 +correctness. Because really, the correctness of Rune is + +00:17:58.720 --> 00:18:00.999 +whatever Emacs does, because there's no official spec on + +00:18:01.000 --> 00:18:04.079 +how things should behave. To do this, we can go look at + +00:18:04.080 --> 00:18:07.159 +the Rust function signature. We know what the arguments + +00:18:07.160 --> 00:18:09.319 +are, we know how many they are, and we know what types they + +00:18:09.320 --> 00:18:11.679 +should be. Given that information, we can generate a + +00:18:11.680 --> 00:18:15.279 +whole bunch of random functions feeding those types in. And + +00:18:15.280 --> 00:18:18.959 +then we send a copy over to Emacs, we send a copy over to Rune. + +00:18:18.960 --> 00:18:21.679 +They each evaluate it and they return the result and we make + +00:18:21.680 --> 00:18:23.519 +sure the results are the same. Then you do that for + +00:18:23.520 --> 00:18:26.199 +thousands of different implementations of the function. + +00:18:26.200 --> 00:18:29.039 +And it helps us find corner cases really easy without having + +00:18:29.040 --> 00:18:31.639 +to handwrite a whole bunch of different cases to test things + +00:18:31.640 --> 00:18:36.344 +and say, where are these two functions different? + +NOTE Status + +00:18:36.345 --> 00:18:39.359 +So the current status: we already have a multi-threaded Elixir + +00:18:39.360 --> 00:18:42.999 +interpreter and bytecode engine inside there. There's no + +00:18:43.000 --> 00:18:45.679 +actual text editor in there yet, but the primitives are + +00:18:45.680 --> 00:18:48.679 +there. Like you can insert text, move point around, + +00:18:48.680 --> 00:18:52.039 +delete text, do different things like that. But we don't + +00:18:52.040 --> 00:18:53.679 +have a GUI hooked up to different key bindings to actually + +00:18:53.680 --> 00:18:58.159 +type on. There's just a REPL to operate in. We have about + +00:18:58.160 --> 00:19:01.279 +250 of the 1500 built-in functions already implemented + +00:19:01.280 --> 00:19:04.119 +inside there. There's a lot of low-hanging fruit inside this + +00:19:04.120 --> 00:19:07.246 +area to still be implemented. + +NOTE Next directions + +00:19:07.247 --> 00:19:07.719 +The next directions we're + +00:19:07.720 --> 00:19:11.959 +working on is we're optimizing the GC. We want to make it + +00:19:11.960 --> 00:19:13.839 +generational. Like I said, right now, it's just a simple + +00:19:13.840 --> 00:19:17.359 +semi-spaced copying GC. We want to add a proper GUI. We need + +00:19:17.360 --> 00:19:19.599 +to implement text properties, overlays, process and job + +00:19:19.600 --> 00:19:22.738 +control, all that goodness right there. + +NOTE How to get involved + +00:19:22.739 --> 00:19:25.378 +How can you get involved? This is hosted on GitHub. + +00:19:25.379 --> 00:19:26.424 +You can come on over. + +00:19:26.425 --> 00:19:28.639 +If you have any ideas about how to implement something or + +00:19:28.640 --> 00:19:30.639 +something you'd like to see done, go ahead and just open an + +00:19:30.640 --> 00:19:32.799 +issue so we can have a discussion about it. We've had lots of + +00:19:32.800 --> 00:19:34.599 +interesting discussions with different people coming in + +00:19:34.600 --> 00:19:37.639 +to the GitHub repo. If you're interested in contributing, + +00:19:37.640 --> 00:19:40.439 +the easiest way is probably to run elprop, pick some + +00:19:40.440 --> 00:19:43.279 +function, run elprop on it. I promise it won't take long to + +00:19:43.280 --> 00:19:45.639 +find some issues, some discrepancy between Emacs and Rune, + +00:19:45.640 --> 00:19:48.959 +and that lets you dive into the Rust code and figure out, and + +00:19:48.960 --> 00:19:50.879 +the C code, and figure out what the difference is between the + +00:19:50.880 --> 00:19:53.119 +two. or come along and help implement your favorite + +00:19:53.120 --> 00:19:55.679 +functionality. This has been a really interesting project + +00:19:55.680 --> 00:19:58.359 +so far, and we've had a handful of different contributors on + +00:19:58.360 --> 00:20:01.799 +it who just kind of want to learn Rust or get more into + +00:20:01.800 --> 00:20:06.000 +systems-level programming. Thank you. |