Code at the speed of thought – Zed is a high-performance, multiplayer code editor from the creators of Atom and Tree-sitter.
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Max Brunsfeld f128cf4a33
Defer scanning some worktree subdirectories until they are expanded in the project panel (#2622)
Closes
https://linear.app/zed-industries/issue/Z-352/high-memory-usage-from-fs-scanning-if-project-contains-symlinks-that

### Background

Currently, when you open a project, Zed eagerly scans the directory,
building an in-memory representation of all of the files and directories
within. This scanning includes all git-ignored files and follows any
symlinks. When any directory changes on disk, Zed recursively rescans it
in order to keep its in-memory representation up-to-date. When
collaborating, all of these files are replicated to all guests.

Right now, there are some performance problems associated with the
maintenance of this filesystem state:
* For various reasons, some projects contain symlinks that point out to
large folders like `$HOME`, which itself contains many symlinks that
point to the same large directory. When these projects are opened, the
worktree scans endlessly, using more and more memory.
* Some git-ignored directories (like `target` in a rust project) contain
*many* more files than are actually tracked in the git repository. These
files often change as a result of saving, (e.g. because the compiler
runs). Maintaining in memory all of these paths isn't useful to the
user, and causes significant CPU usage on every save. Most importantly,
when collaborating sending all of these changes to guests can be slow,
and can delay all other RPC messages.

### Change

This PR changes the worktree's filesystem-scanning logic to be *lazy*
about scanning two types of directories:
* git ignored directories
* "external" directories (those that are canonically located outside of
the worktree root, but accessed via symlinks)

The laziness works as follows. When, during a recursive scan, a
directory is found that falls into one of the above 2 categories, that
directory is marked as "unloaded". The directory might later be scanned,
if some explicit operation is performed within it (like opening a
buffer, or creating a file), if any collaborator expands that directory
in their project panel, or if an LSP requests that it be watched.

### Results

When collaborating on the `zed` folder:

| metric | before | after |
|-------|--------|------|
| # `worktree_entries` in collab db initially | 154,763 |  77,679 |
| # `worktree_entries` in collab db after 5 saves | 181,952 | 77,679
(nothing new to scan) |
| app memory footprint (host) | 260MB | 228.5 MB  |

The db thing is a win, because reading and writing to the
`worktree_entries` table is one of the most expensive thing that the
`collab` server does.

There's also generally lower background CPU usage after every save,
because we don't need to recursively rescan directories inside of
`target`.

### Limitations

We still end up scanning some unnecessary directories (like
`target/debug/build/zed-b612db829aeac16e/out`) because the LSP instructs
us to watch those.

### To do:

* [x] Expand parent directories of any path opened via LSP
* [x] Avoid creating orphaned entries when FS events happen inside of
unscanned directories
* [x] Scan any newly-non-ignored directories after gitignore changes
* [x] Emit correct events for newly-discovered paths when expanding dirs
* [x] GC the set of expanded directory ids when dirs are removed
* [x] Don't include "external" entries in file-finder
* [x] Expand any directories watched by LSP
* [ ] manual testing and profiling

### Release Notes:

- Fixed a bug where Zed would use excessive memory when a project folder
contained symlinks pointing to directories outside of the project.
- Reduced Zed's memory and CPU usage when working in folders containing
many git-ignored files.
2023-06-27 17:07:23 -07:00
.cargo Use xtask for theme generation 2023-06-21 18:48:09 +02:00
.github Use nextest instead of test (#2639) 2023-06-22 16:50:26 +02:00
.vscode
assets vim: indent/outdent (#2644) 2023-06-27 04:15:55 -06:00
crates Defer scanning some worktree subdirectories until they are expanded in the project panel (#2622) 2023-06-27 17:07:23 -07:00
docs Update local-collaboration.md 2023-06-27 10:52:38 -04:00
plugins Use the same serde version across the entire workspace 2023-03-28 09:42:00 -07:00
script Update bundle 2023-06-14 17:37:47 -07:00
styles Fix incorrect ThemeAppearance (#2645) 2023-06-26 13:20:32 -04:00
.dockerignore
.gitignore Merge branch 'main' into sergey/z-2308-create-a-proof-of-concept-of-exporting-a-type-from-rust-and 2023-06-22 17:58:56 +02:00
.gitmodules
Cargo.lock Merge remote-tracking branch 'origin/main' into save-conversations 2023-06-23 09:09:42 +02:00
Cargo.toml Z-2308 - Export Theme Types from Rust (#2621) 2023-06-22 12:33:18 -04:00
Dockerfile chore: bump MSRV to 1.70, add rust-toolchain (#2580) 2023-06-06 23:49:34 +02:00
Procfile
README.md Clarify GH Token scope requirements 2023-05-02 12:12:57 +03:00
rust-toolchain.toml chore: add targets to rust-toolchain.toml (#2581) 2023-06-07 00:12:47 +02:00

Zed

CI

Welcome to Zed, a lightning-fast, collaborative code editor that makes your dreams come true.

Development tips

Dependencies

  • Install Postgres.app and start it.

  • Install the LiveKit server and the foreman process supervisor:

    brew install livekit
    brew install foreman
    
  • Ensure the Zed.dev website is checked out in a sibling directory:

    cd ..
    git clone https://github.com/zed-industries/zed.dev
    
  • Initialize submodules

    git submodule update --init --recursive
    
  • Set up a local zed database and seed it with some initial users:

    Create a personal GitHub token to run script/bootstrap once successfully: the token needs to have an access to private repositories for the script to work (repo OAuth scope). Then delete that token.

    GITHUB_TOKEN=<$token> script/bootstrap
    

Testing against locally-running servers

Start the web and collab servers:

foreman start

If you want to run Zed pointed at the local servers, you can run:

script/zed-with-local-servers
# or...
script/zed-with-local-servers --release

Dump element JSON

If you trigger cmd-alt-i, Zed will copy a JSON representation of the current window contents to the clipboard. You can paste this in a tool like DJSON to navigate the state of on-screen elements in a structured way.

Licensing

We use cargo-about to automatically comply with open source licenses. If CI is failing, check the following:

  • Is it showing a no license specified error for a crate you've created? If so, add publish = false under [package] in your crate's Cargo.toml.
  • Is the error failed to satisfy license requirements for a dependency? If so, first determine what license the project has and whether this system is sufficient to comply with this license's requirements. If you're unsure, ask a lawyer. Once you've verified that this system is acceptable add the license's SPDX identifier to the accepted array in script/licenses/zed-licenses.toml.
  • Is cargo-about unable to find the license for a dependency? If so, add a clarification field at the end of script/licenses/zed-licenses.toml, as specified in the cargo-about book.

Wasm Plugins

Zed has a Wasm-based plugin runtime which it currently uses to embed plugins. To compile Zed, you'll need to have the wasm32-wasi toolchain installed on your system. To install this toolchain, run:

rustup target add wasm32-wasi

Plugins can be found in the plugins folder in the root. For more information about how plugins work, check the Plugin Guide in crates/plugin_runtime/README.md.