Excessive RAM usage / crash on Linux: webkit2gtk-4.0 2.47.x (unstable) + Tauri 1.x incompatibility on Fedora 42

[ddaikodaiko]

Environment

Field	Value
OS	Fedora 42 (Linux 6.19.14-101.fc42.x86_64)
Phoenix Code	Desktop app (binary from installer)
Tauri version	1.8.1 (embedded in binary)
webkit2gtk linked	libwebkit2gtk-4.0.so.37
webkit2gtk-4.0 version	2.47.2-3.fc42
webkit2gtk-4.1 version	2.52.3-1.fc42 (available but unused)

Problem

Phoenix Code consumes an extreme amount of RAM — often 700 MB–1.4 GB — and crashes/freezes the system, especially at startup when loading the editor.

Root Cause

This is a triple compatibility problem:

1. webkit2gtk-4.0 2.47.x is an unstable/development release

In GNOME/WebKit versioning, odd minor versions are development branches:

• 2.46.x → stable (production)
• 2.47.x → unstable/development ← what Fedora 42 ships
• 2.48.x → next stable

Fedora 42 is a cutting-edge distro that has already moved webkit2gtk4.0 to the 2.47.x development branch. This version introduces a new GPU process architecture and DMA-buf renderer that has known memory regressions on Linux/GTK, including:

• DMA-buf renderer allocating GPU buffers that aren't properly released
• GPU compositing layer memory not being freed under memory pressure
• JavaScriptCore concurrent JIT accumulating compilation buffers during heavy JS load (like loading the full editor at startup)

2. Tauri 1.x cannot use the stable webkit2gtk-4.1

Phoenix Desktop uses Tauri 1.8.1, which only supports the webkit2gtk-4.0 API (GTK3). Tauri 2.x migrated to webkit2gtk-4.1 (GTK4), which is available in stable form on Fedora 42 (2.52.3). Since Phoenix hasn't migrated to Tauri 2 yet, it's forced to use the unstable 2.47.x webkit.

3. Heavy JS load amplifies the problem

The editor loads the full Brackets-based codebase as a single SPA in the WebView, with a large JS heap. This creates significant pressure on JavaScriptCore's JIT compiler exactly when webkit2gtk 2.47.x is least stable.

Memory breakdown (approximate)

Component	Without workaround	With workaround
WebKit DMA-buf GPU buffers	300–600 MB	~0
Compositing layers	150–300 MB	~0
JS heap (editor)	200–400 MB	200–400 MB
phnode (Node.js)	50–100 MB	50–100 MB
Total	~700 MB – 1.4 GB	~300–500 MB

Workaround (temporary)

Adding these environment variables to the launcher script (phcode.sh) significantly reduces memory usage:

#!/bin/bash
export WEBKIT_DISABLE_DMABUF_RENDERER=1
export WEBKIT_DISABLE_COMPOSITING_MODE=1
export JSC_useConcurrentJIT=0
/home/user/.phoenix-code/phoenix-code "$@"

• WEBKIT_DISABLE_DMABUF_RENDERER=1 — disables the DMA-buf renderer that leaks in 2.47.x
• WEBKIT_DISABLE_COMPOSITING_MODE=1 — disables GPU compositing, saves ~150–300 MB
• JSC_useConcurrentJIT=0 — disables concurrent JIT, prevents buffer accumulation at startup

The installer could include these by default on Linux when webkit2gtk-4.0 < 2.48.0 is detected.

Proper fix

Migrate Phoenix Desktop from Tauri 1.x → Tauri 2.x. Tauri 2 uses webkit2gtk-4.1, which has a stable, modern version (2.52.3) on Fedora 42 and avoids this entire class of issues.

Relevant: https://v2.tauri.app/start/migrate/

Additional notes

• The phcode.sh launcher script generated by the installer is empty (just calls the binary), so users have no way to set these flags without modifying it manually.
• Also found minor memory leaks in src-node (pendingExecPromiseMap without timeout in node-connector.js, queuedReq Map not cleared on ESLint process restart in ESLint/service.js), but these are secondary compared to the WebKit issue above.

[abose]

We are currently overhauling the Linux builds to move to chromium based engine instead of webkit in Linux, and the new version should be out in a week. (Check this bug report and this discussion thread for more info.)

In the meantime, you can use the 5.1.3 pre-release build. Please check that out and see if it works for you.

related to: #2890