base on Emacs LSP performance booster # Emacs LSP performance booster   Improve the performance of [lsp-mode](https://github.com/emacs-lsp/lsp-mode) or [eglot](https://github.com/joaotavora/eglot) using a wrapper executable. ## Background & Prior work (Huge thanks to @yyoncho for both maintaining lsp-mode and giving me the inspiration of this project). According to [yyoncho](https://www.reddit.com/r/emacs/comments/ymrkyn/comment/iv90q4i/?utm_source=share&utm_medium=web2x&context=3), the are several performance issues related to lsp-mode (mostly the same for eglot): 1. Json parsing in Emacs is slow 2. The server may block on sending data to emacs when the buffer is full, because Emacs is consuming the data too slowly 3. Similarly, Emacs may block while attempting to send data to the server (hence blocking the Emacs UI), because the server may be busy @yyoncho tried to solve these issues by implementing a [native async non-blocking jsonrpc](https://github.com/emacs-lsp/emacs) fork of emacs. The result is very good regarding performance. However, it requires modifications in the Emacs source code and it seems unlikely that those changes could be merged upstream. Also, it could prove difficult to maintain, since it also requires a separate code path in lsp-mode (I myself encountered some [issues](https://github.com/emacs-lsp/emacs/issues/12)). ## How this project works This project provides a wrapper-executable around lsp server programs, to work around the above-mentioned issues: - It converts json messages from the server at high speed directly into **elisp bytecode** (in text representation) for Emacs to read. * e.g. `{"objs":[{"a":1},{"a":2}]}` would be converted to `#[0 "\301\302\300\303D\300\304D\"D\207" [:a :objs vector 1 2] 13]` * This improves the message parsing performance in Emacs by ~4x for large json objects; see benchmark result [here](https://github.com/blahgeek/emacs-lsp-booster/actions/runs/7416840025/job/20182439682#step:5:142) * Although Emacs still needs to parse the text representation and interpret it into elisp objects, the performance gain mainly comes from the following: * Parsing (`read`ing) elisp object is apparently better optimized and simpler in Emacs * By using bytecode to construct objects, we can eliminate duplicated objects (e.g. the "a" json key in above example) - It separates reading and writing into different threads and keeps pending messages in internal buffers within each thread, to avoid blocking on IO. This solves issues (2) and (3) mentioned above. Overall, this _lsp server wrapper_ strategy achieves similar result as the native async non-blocking jsonrpc approach without requiring modifications in Emacs source code. > [!IMPORTANT] > At present only local lsp server programs which communicate by standard input/output can be wrapped, not servers communicating over network ports (local or remote). ## How to use Generally, what you need to do is: 1. Wrap your lsp server command with this `emacs-lsp-booster` executable. For example, if the original lsp server command is `pyright-langserver --stdio`, configure lsp-mode or eglot to run `emacs-lsp-booster [flags --] pyright-langserver --stdio` instead. 2. Advise or update the json parsing function in `lsp-mode` or `eglot` to parse any bytecode input seen, prior to parsing it as json. See more detailed configuration steps below. ### Obtain or build `emacs-lsp-booster` For Linux or Windows users, you may download the prebuilt binary from [release](https://github.com/blahgeek/emacs-lsp-booster/releases). *(The macOS binary in the release page lacks proper code signing for now.)* A flake for nix users is available [here](https://github.com/slotThe/emacs-lsp-booster-flake). Alternatively, you may build the target locally: 1. Setup [Rust toolchain](https://www.rust-lang.org/tools/install) 2. Run `cargo build --release` 3. Find the built binary in `target/release/emacs-lsp-booster` Then, put the `emacs-lsp-booster` binary in your $PATH (e.g. `~/.local/bin`). ### Configure `lsp-mode` > [!NOTE] > Make sure NOT to use the [native-jsonrpc custom version](https://github.com/emacs-lsp/emacs) of Emacs 1. **Use [plist for deserialization](https://emacs-lsp.github.io/lsp-mode/page/performance/#use-plists-for-deserialization) for lsp-mode** 3. Add the following code to your `init.el`: ```elisp (defun lsp-booster--advice-json-parse (old-fn &rest args) "Try to parse bytecode instead of json." (or (when (equal (following-char) ?#) (let ((bytecode (read (current-buffer)))) (when (byte-code-function-p bytecode) (funcall bytecode)))) (apply old-fn args))) (advice-add (if (progn (require 'json) (fboundp 'json-parse-buffer)) 'json-parse-buffer 'json-read) :around #'lsp-booster--advice-json-parse) (defun lsp-booster--advice-final-command (old-fn cmd &optional test?) "Prepend emacs-lsp-booster command to lsp CMD." (let ((orig-result (funcall old-fn cmd test?))) (if (and (not test?) ;; for check lsp-server-present? (not (file-remote-p default-directory)) ;; see lsp-resolve-final-command, it would add extra shell wrapper lsp-use-plists (not (functionp 'json-rpc-connection)) ;; native json-rpc (executable-find "emacs-lsp-booster")) (progn (when-let ((command-from-exec-path (executable-find (car orig-result)))) ;; resolve command from exec-path (in case not found in $PATH) (setcar orig-result command-from-exec-path)) (message "Using emacs-lsp-booster for %s!" orig-result) (cons "emacs-lsp-booster" orig-result)) orig-result))) (advice-add 'lsp-resolve-final-command :around #'lsp-booster--advice-final-command) ``` Done! Now try to use lsp-mode as usual. ### Configure `eglot` Please see https://github.com/jdtsmith/eglot-booster for information on configuring `eglot`. Huge thanks to @jdtsmith ### How to verify it's working 1. Check that `emacs-lsp-booster` process is running 2. Check the stderr buffer (e.g. for lsp-mode, `*pyright::stderr*` buffer; for eglot, the ` EGLOT (...) stderr*` buffer, note the leading space); it should contain `emacs_lsp_booster` related log. ### Advanced usage Run `emacs-lsp-booster --help` for more options. ", Assign "at most 3 tags" to the expected json: {"id":"6804","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"