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Hyrule Warriors: fix the map's one-frame UI flash and movie stutter - #861
I have read and followed the Coding Guidelines to the best of my ability.
I have put [HUMANMADE] in the title if the pr was human-mande
Summary
Two Hyrule Warriors: Age of Imprisonment fixes, one commit each.
1. Map: one frame of black tiles and missing text when the cursor leaves a mission node
Each time the cursor leaves a mission node on the map, exactly one frame shows opaque black tiles in the top bar, a black strip in the bottom bar, and missing icons and text.
Why it happens. A Switch 2 GPU starts on a command list some time after the game submits it, and the game relies on that: it writes the vertices and indices of new UI labels 0.5-2 ms after submitting the draws that use them. When our GPU thread has caught up with the game, it uploads those buffers half written. Found with EDEN_NX2_HAZARD's present-time content recheck, which only fires in the bad frames, at buffer_cache.h's index and vertex uploads. Delaying submissions by 2 ms or more removes the flash; 1 ms and 0.5 ms don't.
What this changes (video_core/nx2_gpu_latency.h, gpu_thread.*, plus three one-line hooks):
The GPU thread holds each command list until it is 3 ms old (EDEN_NX2_GPU_LATENCY_US, 0 turns it off), or until a game thread blocks on the GPU (frame fence waits, waits for the back thread, nvhost event waits), since then the game isn't writing. A list that has already queued that long runs at once.
The hold is only on while the game is paced to every 2nd or 3rd vblank (30 or 20 fps), where it takes time the game would otherwise sleep. Held on every frame, it cost about 3 fps in a Hyrule fight (48.9 -> 45.9 fps mean over 3 runs each), where the game, the GPU thread and the back run one after another and the GPU thread is usually idle when a list arrives. With the gate, the hold never turns on in fights or in 60 fps scenes. If frames fall out of that pacing while it is on, it turns off and waits twice as long (up to about 30 s) before trying again.
2. Movies stutter after a minute or two while the fps counter stays steady
Hyrule's movies (title screen, cutscenes) start to stutter after a minute or two of playback while the game keeps drawing a steady 30 fps. The frames are thrown away by our own movie pacing (DropOvertakenFrames, added for Ocarina of Time in 1f52ac7). The decoder log counts them as "late dropped": in one tester's log 2115 of 5444 frames of a 3-minute cutscene, and 784 of 1384 in another stretch. With EDEN_NX2_VDEC_PACE=0 the same movies play smoothly.
Why it happens. The pacing is built for clients like OoT, which show one decoded frame per frame they draw. Hyrule's player queues movie frames ahead (it holds 7 of its 8 output images) and shows each one at its own time. Dropping frames for it only hands it frames earlier than it wants, so it holds each one longer and takes fewer. On top of that, the movie clock moved earlier whenever a frame was acquired "early", and a frame handed out right after a drop is early only because of the drop. So the drops fed themselves until about every other frame was gone.
What this changes (core/hle/service/nx2_gsv.h):
Frames are only dropped while the client holds at most 2 output images. OoT has 2, so its behaviour is unchanged; Hyrule, which holds 7, keeps pace itself.
A frame handed out right after a drop no longer moves the clock earlier.
Nothing is dropped while the next frame comes before the last one acquired (the movie looped or jumped back). Before this, the title movie lost 30 frames (MaxDroppedInARow) at every loop.
The decoder log line also says how many images the client holds, e.g. 0 late dropped, client holds 7 of 8 images.
Type of change
Bug fix
Game compatibility / game-support
Performance
New feature
Refactor / cleanup
CI / build
Documentation
Related issues
None
Testing
Tested on Windows
Tested on Linux
Tested on macOS
Tested on NVIDIA
Tested on AMD
Tested on Intel
Games tested:
Hyrule Warriors: Age of Imprisonment (update 196608), map, 8 node departures per run (eden-cli, frame capture of every present): one bad frame per departure before; 0 bad frames in every run with the change (5 runs across the final gate and a near-identical earlier one).
Hyrule Warriors, fight (t 150-290 s of a recorded route): 48.1 fps mean with and without the change; the hold never turned on. MKW time trial: unchanged, the hold never turned on.
Hyrule Warriors, title movie left running in the Qt build: 0 frames dropped over 6 minutes (10200 frames, including a loop), against 843 by the same point without the movie change. No visible stutter.
Ocarina of Time, opening movie (eden-cli, 90 s): still drops frames while the game runs slow (302 during its slow start), then keeps pace; the client holds 1 of 2 images.
Checklist
I built it locally and it compiles without new warnings
I did not add any copyrighted game data, keys or firmware
Hyrule Warriors' movies stutter after a minute or two while the game
keeps drawing a steady 30 fps: the decoder log counts thousands of late
dropped frames (57% of them in one tester's log). The game queues
movie frames ahead (it holds 7 of its 8 output images) and shows each
at its own time. Dropping frames for it only hands it frames earlier
than it wants, so it holds them longer and takes fewer, and the clock
followed those early frames, so the drops fed themselves. With
EDEN_NX2_VDEC_PACE=0 the same movies play smoothly.
- Only drop frames while the client holds at most 2 output images.
Ocarina of Time, which the pacing is for, has 2, so it is unchanged.
- A frame handed out right after a drop no longer moves the clock
earlier.
- Don't drop when the next frame comes before the last one acquired
(the movie looped or jumped back). The title movie lost 30 frames at
every loop until the client re-anchored the clock.
- The decoder log line shows how many images the client holds.
Tested on Hyrule's title movie (GUI, 6 min: 0 dropped, previously 843)
and Ocarina of Time's opening movie (still drops while the game runs
slow, then keeps pace).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YQZoXmAUTth3PtUD1X3sFH
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Walkthrough
The change adds GPU latency tracking based on frame presents and guest waits. It can delay eligible GPU command lists and changes decoder frame-drop and output-clock handling based on PTS values and client-held images.
Changes: Frame pacing
Layer / File(s)
Summary
Latency state and event sampling src/video_core/nx2_gpu_latency.h, src/core/hle/service/nvdrv/devices/nvhost_ctrl.cpp, src/core/hle/service/nx2_gsv.h, src/video_core/CMakeLists.txt
A rolling sample of present intervals controls steady mode. Present and guest-wait paths update latency state. The header is added to the video_core source list.
GPU command-list hold src/video_core/gpu_thread.h, src/video_core/gpu_thread.cpp
Submitted command lists record a timestamp and guest-wait count. The GPU thread delays eligible submissions while steady mode is active and exits the hold when guest waits change or the thread is asked to stop.
Decoder output and frame dropping src/core/hle/service/nx2_gsv.h
Decoder outputs carry drop history. Frame dropping considers earlier PTS values and client-held image counts. Output-clock anchoring uses the drop history, and logging reports held and registered images.
sequenceDiagram
participant Nx2Gsv
participant NvhostCtrl
participant Nx2GpuLatency
participant ThreadManager
Nx2Gsv->>Nx2GpuLatency: Record presents and guest waits
NvhostCtrl->>Nx2GpuLatency: Record guest waits
ThreadManager->>Nx2GpuLatency: Read pacing state and guest-wait count
ThreadManager->>ThreadManager: Hold eligible command list, then dispatch
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Suggested reviewers:takoroka, kraibse
Merge Risk: Low · previous review 17478
This change adds a short GPU hold and adjusts movie frame dropping for Hyrule Warriors under 30/20 fps pacing. The remaining issues are minor pacing quirks: stale controller state between sessions, early release on nonblocking polls, and extra hold on synchronous submissions. Merging is reasonable with follow-up.
Security architecture risk: Minimal · up to 17478
The changes affect scheduling and movie playback, but the inspected paths do not establish a new security, isolation, ownership, or failure-containment risk. The added GPU delay has a deadline and early-exit conditions.
Retained concerns
No architecture-level concerns identified.
Security review details
Security Blast Radius
inferred — The added wait signal is process-wide rather than channel-scoped, so a guest wait can release latency holds for other queued channels using the same GPU consumer. The inspected consequence is shared scheduling influence, not access to another channel's data or authority.
Trust Boundaries and Controls
inferred — Guest-controlled wait activity can shorten the new hold, but the counter does not select buffers or bypass fence completion. Removing the hold returns dispatch toward pre-PR timing; it does not satisfy the underlying GPU synchronization condition.
Resilience and Maintainability Implications
observed — The hold checks shutdown and guest-wait changes while waiting for its configured deadline. The cadence estimator uses fixed-size storage and bounded backoff. Its static state is not reset alongside the existing session-level NX2 gate, allowing pacing history to carry into a later session without establishing an unbounded wait.
inferred — The new held-image estimate relies on uniqueness in an existing guest-driven free-image queue. Duplicate releases can reduce the estimate and re-enable dropping. Duplicate insertion was already possible at the base; the newly supported consequence is inaccurate pacing, not an established expansion of image ownership or host access.
Pre-merge checks: 4
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Title check
The title names the two user-visible problems the PR targets: a one-frame UI flash on the Hyrule Warriors map and movie stutter. The changeset matches both. It adds GPU command-list holding under 30/2…
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Full details: Title check
Explanation
The title names the two user-visible problems the PR targets: a one-frame UI flash on the Hyrule Warriors map and movie stutter. The changeset matches both. It adds GPU command-list holding under 30/20 fps pacing (gpu_thread, nx2_gpu_latency, nvhost_ctrl) and movie-frame drop and clock changes in nx2_gsv.h. The title does not mention the GPU latency gate or the movie decoder change by name, but it covers the main purpose of the change.
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Actionable comments posted: 3
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at @src/core/hle/service/nvdrv/devices/nvhost_ctrl.cpp:
- Line 136: Update the notification around
VideoCommon::Nx2GpuLatency::NoteGuestWait() so nonblocking fence polls with
params.timeout == 0 that do not enter WaitHost() do not increment the wait
counter; preserve the notification when check_failing() actually calls
WaitHost().
Review comments at @src/video_core/gpu_thread.cpp:
- Around line 254-255: Update the SubmitListCommand handling around
HoldForGpuLatency so blocking submissions do not incur the latency hold: check
the command’s existing blocking state and skip the hold when the submitting
thread already waits for execution. Preserve the hold behavior for asynchronous
submissions; only publish a wait through the existing mechanism if that is
required to support blocking submissions safely.
Review comments at @src/video_core/nx2_gpu_latency.h:
- Around line 64-67: Add a reset operation for the NX2 pacing controller that
clears its function-local state, including the cooldown, samples, and prior
activation state; locate that state in the function containing `last`,
`intervals`, `count`, and `need`. Call the reset alongside the other NX2 session
resets in the session-reset flow in `nvdrv.cpp`.
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…0 fps
A Switch 2 GPU starts on a command list some time after the game submits
it, and games rely on that. Hyrule Warriors: Age of Imprisonment writes the
vertices and indices of new UI labels 0.5-2 ms after submitting the draws
that use them; when the GPU thread had caught up it uploaded them half
written, so the map showed one frame of black tiles in the top and bottom
bars and missing icons and text each time the cursor left a mission node.
Hold each list until it is 3 ms old (EDEN_NX2_GPU_LATENCY_US, 0 turns it
off), or until a game thread blocks on the GPU (frame fence waits, waits
for the back thread, nvhost event waits), since then it isn't writing.
The hold is only on while the game is paced to every 2nd or 3rd vblank
(30 or 20 fps: the median of the last 60 frame intervals within 1.5 ms of
it, 54 of 60 within 4 ms). The game then sleeps for vblank, and the hold
takes time it would otherwise wait. Held on every frame, it cost about
3 fps in a Hyrule fight, where the game, the GPU thread and the back run
one after another. If frames fall out of that pacing while the hold is on,
it turns off and waits twice as long (up to about 30 s) before retrying.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YQZoXoAgfwVxE9CD2QhStD
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Summary
Two Hyrule Warriors: Age of Imprisonment fixes, one commit each.
1. Map: one frame of black tiles and missing text when the cursor leaves a mission node
Each time the cursor leaves a mission node on the map, exactly one frame shows opaque black tiles in the top bar, a black strip in the bottom bar, and missing icons and text.
Why it happens. A Switch 2 GPU starts on a command list some time after the game submits it, and the game relies on that: it writes the vertices and indices of new UI labels 0.5-2 ms after submitting the draws that use them. When our GPU thread has caught up with the game, it uploads those buffers half written. Found with
EDEN_NX2_HAZARD's present-time content recheck, which only fires in the bad frames, atbuffer_cache.h's index and vertex uploads. Delaying submissions by 2 ms or more removes the flash; 1 ms and 0.5 ms don't.What this changes (
video_core/nx2_gpu_latency.h,gpu_thread.*, plus three one-line hooks):EDEN_NX2_GPU_LATENCY_US,0turns it off), or until a game thread blocks on the GPU (frame fence waits, waits for the back thread, nvhost event waits), since then the game isn't writing. A list that has already queued that long runs at once.2. Movies stutter after a minute or two while the fps counter stays steady
Hyrule's movies (title screen, cutscenes) start to stutter after a minute or two of playback while the game keeps drawing a steady 30 fps. The frames are thrown away by our own movie pacing (
DropOvertakenFrames, added for Ocarina of Time in 1f52ac7). The decoder log counts them as "late dropped": in one tester's log 2115 of 5444 frames of a 3-minute cutscene, and 784 of 1384 in another stretch. WithEDEN_NX2_VDEC_PACE=0the same movies play smoothly.Why it happens. The pacing is built for clients like OoT, which show one decoded frame per frame they draw. Hyrule's player queues movie frames ahead (it holds 7 of its 8 output images) and shows each one at its own time. Dropping frames for it only hands it frames earlier than it wants, so it holds each one longer and takes fewer. On top of that, the movie clock moved earlier whenever a frame was acquired "early", and a frame handed out right after a drop is early only because of the drop. So the drops fed themselves until about every other frame was gone.
What this changes (
core/hle/service/nx2_gsv.h):MaxDroppedInARow) at every loop.0 late dropped, client holds 7 of 8 images.Type of change
Related issues
None
Testing
Games tested:
Checklist
🤖 Generated with Claude Code
https://claude.ai/code/session_01YQZoXoAgfwVxE9CD2QhStD
Summary by CodeRabbit