seeddsandRAHUL REX
82ab25b40b
present_now cycles three Metal 4 command allocators by ticket, and before resetting one it waited for g_pq_done to reach the ticket that last used it. g_pq_done is not GPU completion: every display-link callback sets it to ticket - 1 before presenting (the previous present was committed, not run), and a present that was not submitted sets it to its own ticket. So a display-link present never waited there: with three presents in flight, or two after a dropped frame, the allocator was reset and its command buffer and UV buffer encoded again under a present the GPU had not run. Each allocator now keeps the newest ticket its own commit feedback reported (g_present_alloc_done), and its reuse waits for that. The display-link callback can now block in present_now until the GPU has run that allocator's previous present; it still moves g_pq_done before it waits, so the game's swapchain acquire is unchanged. General: every game presents through this path, display-link mode is the default.
t_present_alloc holds the Metal 4 queue behind a shared event and calls the display-link callback by hand, each present with a drawable of its own offscreen layer: a dropped frame (tickets 1, 3, then 4 on allocator 1 again) and one frame per tick (5, 6, 7, then 8 on allocator 2 again). Checked on an Apple M6 at 6062518: without the production change 4 of 13 checks fail in 10 of 10 runs, the earlier drawable reads back 0 in all 64 pixels, and every run logs [RED] display command buffer error with kIOGPUCommandBufferCallbackErrorPageFault; with it 13 of 13 pass in 20 of 20 runs under MTL_DEBUG_LAYER=1 with no red line. The whole dm/gfx/tests run list passes, dmhost builds for Mario, docs tests pass. Not checked: a game run that hits it, the iPhone, the not-submitted path. Docs: the frame-rate reference entry (with the page-fault symptom) and the symptom index.
Co-Authored-By: RAHUL REX <75500427+RahulRex0@users.noreply.github.com>
Subsystem references
How the host meets each part of a Switch game, and every failure met so far, one entry per mechanism: symptom, cause, fix (file and function), the games it was found on (linked to their notes in dm/games/<id>/README.md). Start from the symptom index when you have a log line or a visible result; the workflows that lead here are in docs/agents.
| File | Covers |
|---|---|
| packing.md | NSP script, compressed inputs and build artifacts |
| rewriter.md | The NSO rewriter patch_nso.py: jump tables, exclusive windows, patch area reach, cuts and observation gates, functions without unwind entries, stack and system registers, relocations |
| memory.md | Guest layout, heap and application pool, virtual address memory and the alias region (the SDK's node area), engine allocators, mapping SVCs, running out of memory |
| threads.md | Thread creation and cores, address arbitration, yields and spin waits, events |
| services.md | SDK calls and system services: sm connections, names that changed between SDKs, file system and saves, add-on content, input, keyboard and applets, display and operation mode, accounts and network, settings and fonts, C library and time, modules |
| movies.md | The SDK's movie library: decoder lifecycle, output slots, native-texture output, demuxers and codecs, game movie players |
| audio.md | The audio renderer and its command lists by SDK, AudioOut and devices, codecs, timing |
| frame-rate.md | The host's frame step, engine frame limiters, present intervals and display rates, CPU cost |
| nvn-objects.md | NVN object sizes, memory pools, command memory, queues and syncs, CPU-written textures, NVN entry points |
| rendering.md | The replay on Metal: textures, passes and clears, blend / depth / stencil, vertex input, uniforms and ordering, conditional rendering; the Vulkan and OpenGL layers |
| shaders.md | Shader containers by engine, control sections and code, translation, bindings and handles, shaders compiled at run time, pipelines and caches |
| game-state.md | Saves, scripted state, and game behaviour that looks like a host bug but is not |
A new general finding goes into the file and section it belongs to, in the same form, with a line in the symptom index; a fact about one game goes into that game's note.