Linux: NVIDIA + Wayland keeps the GPU renderer (__NV_DISABLE_EXPLICIT_SYNC) #24

2026-09-27T22:22:01-04:00

jared commented

2026-09-27 22:22:01 -04:00

NVIDIA + Wayland: keep the GPU renderer (explicit-sync fix)

Why: 4.12.343 made the app launch on NVIDIA + Wayland by disabling WebKit's DMA-BUF renderer and forcing X11. That works, but every frame then goes through shared memory under XWayland, and at 3840×2058 it's noticeably laggy. The reporter traced the real cause with WAYLAND_DEBUG=1:

wl_display#1.error(wp_linux_drm_syncobj_surface_v1#51, 4, "explicit sync is used, but no acquire point is set")
Gdk-Message: Error 71 (Protocol error) dispatching to Wayland display.

It's an explicit-sync bug between WebKit and the NVIDIA driver, not a GBM format/modifier one.

Reporter's test matrix (RTX 3070, driver 615.71.09, Mesa 26.2.3, webkit2gtk 2.52.6, KDE Plasma Wayland, one render node):

Test (all with `LOTUS_NO_GPU_WORKAROUNDS=1`)	Result
native Wayland, nothing else	explicit-sync protocol error, no window
`WEBKIT_DMABUF_RENDERER_DISABLE_GBM=1` (Wayland)	same explicit-sync error
`GDK_BACKEND=x11` + `…DISABLE_GBM=1`	"Failed to import DMABuf" forever, blank window
`WEBKIT_DISABLE_DMABUF_RENDERER=1` (Wayland, no X11)	works (shared memory)
`__NV_DISABLE_EXPLICIT_SYNC=1` (Wayland)	works, GPU renderer, visibly smoother

New defaults (only when the NVIDIA driver is loaded):

Native Wayland: __NV_DISABLE_EXPLICIT_SYNC=1, keeping the GPU (DMA-BUF) renderer.
X11 session, or GDK_BACKEND=x11 set by the user: WEBKIT_DISABLE_DMABUF_RENDERER=1, since the DMA-BUF renderer fails there.
X11 is never forced any more.
LOTUS_GPU_SAFE_MODE=1: opt-in shared-memory rendering on Wayland as a last resort.
LOTUS_NO_GPU_WORKAROUNDS=1, or values the user set: left alone.

One stderr line says what was set. There are 9 unit tests, covering: never forcing X11, a user-forced X11 counting as X11, GDK_BACKEND=wayland,x11, safe mode, user values winning, and the opt-out. clippy is clean.

To verify after merge: the reporter launches the next Arch build with no env vars, expecting native Wayland, the GPU renderer and smooth scrolling.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

## NVIDIA + Wayland: keep the GPU renderer (explicit-sync fix) **Why:** 4.12.343 made the app launch on NVIDIA + Wayland by disabling WebKit's DMA-BUF renderer and forcing X11. That works, but every frame then goes through shared memory under XWayland, and at 3840×2058 it's noticeably laggy. The reporter traced the real cause with `WAYLAND_DEBUG=1`: ``` wl_display#1.error(wp_linux_drm_syncobj_surface_v1#51, 4, "explicit sync is used, but no acquire point is set") Gdk-Message: Error 71 (Protocol error) dispatching to Wayland display. ``` It's an explicit-sync bug between WebKit and the NVIDIA driver, not a GBM format/modifier one. **Reporter's test matrix** (RTX 3070, driver 615.71.09, Mesa 26.2.3, webkit2gtk 2.52.6, KDE Plasma Wayland, one render node): | Test (all with `LOTUS_NO_GPU_WORKAROUNDS=1`) | Result | |---|---| | native Wayland, nothing else | explicit-sync protocol error, no window | | `WEBKIT_DMABUF_RENDERER_DISABLE_GBM=1` (Wayland) | same explicit-sync error | | `GDK_BACKEND=x11` + `…DISABLE_GBM=1` | "Failed to import DMABuf" forever, blank window | | `WEBKIT_DISABLE_DMABUF_RENDERER=1` (Wayland, no X11) | works (shared memory) | | **`__NV_DISABLE_EXPLICIT_SYNC=1` (Wayland)** | **works, GPU renderer, visibly smoother** | **New defaults** (only when the NVIDIA driver is loaded): - **Native Wayland:** `__NV_DISABLE_EXPLICIT_SYNC=1`, keeping the GPU (DMA-BUF) renderer. - **X11 session, or `GDK_BACKEND=x11` set by the user:** `WEBKIT_DISABLE_DMABUF_RENDERER=1`, since the DMA-BUF renderer fails there. - **X11 is never forced** any more. - **`LOTUS_GPU_SAFE_MODE=1`:** opt-in shared-memory rendering on Wayland as a last resort. - **`LOTUS_NO_GPU_WORKAROUNDS=1`, or values the user set:** left alone. One stderr line says what was set. There are 9 unit tests, covering: never forcing X11, a user-forced X11 counting as X11, `GDK_BACKEND=wayland,x11`, safe mode, user values winning, and the opt-out. clippy is clean. **To verify after merge:** the reporter launches the next Arch build with no env vars, expecting native Wayland, the GPU renderer and smooth scrolling. 🤖 Generated with [Claude Code](https://claude.com/claude-code) https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

jared added 1 commit 2026-09-27 22:22:01 -04:00

fix(linux): NVIDIA + Wayland keeps the GPU renderer (explicit-sync fix) bb5364b53c

The 4.12.343 workaround (WEBKIT_DISABLE_DMABUF_RENDERER=1 + GDK_BACKEND=x11)
made the app launch but pushed every frame through shared memory under
XWayland: noticeably laggy at 3840x2058. The reporter's WAYLAND_DEBUG trace
showed the real cause on native Wayland:

  wl_display#1.error(wp_linux_drm_syncobj_surface_v1#51, 4,
    "explicit sync is used, but no acquire point is set")
  Gdk-Message: Error 71 (Protocol error) dispatching to Wayland display.

An explicit-sync bug, not a GBM format/modifier one. Their test matrix
(RTX 3070, driver 615.71.09, webkit2gtk 2.52.6, KDE Wayland):
- __NV_DISABLE_EXPLICIT_SYNC=1 alone: clean, GPU (DMA-BUF) renderer, smooth;
- WEBKIT_DISABLE_DMABUF_RENDERER=1 alone on Wayland: clean (no X11 needed);
- WEBKIT_DMABUF_RENDERER_DISABLE_GBM=1: same explicit-sync error on Wayland,
  "Failed to import DMABuf" under XWayland;
- X11/XWayland with the DMA-BUF renderer: "Failed to create GBM buffer".

New defaults when the NVIDIA driver is loaded:
- native Wayland: __NV_DISABLE_EXPLICIT_SYNC=1, GPU renderer kept;
- X11 session or user-forced GDK_BACKEND=x11: WEBKIT_DISABLE_DMABUF_RENDERER=1;
- never force X11 any more;
- LOTUS_GPU_SAFE_MODE=1: opt-in shared-memory rendering on Wayland too;
- LOTUS_NO_GPU_WORKAROUNDS=1 / user-set values: untouched.
One stderr line says what was set. 9 unit tests.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

jared merged commit 8ee90444ee into main

2026-09-27 22:26:51 -04:00

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Reference: LotusGuild/cinny-desktop#24