WIP: fix(macos): bind a direct draw's 8-bit indices with their size on MoltenVK #678
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Type: fix · Risk: low · Tested on: macOS 26.7.1, Apple M4 Max (MoltenVK 1.4.2), arm64 and x86_64 under Rosetta · Needs: macOS, Apple silicon (a start to play on the rebased stack); Windows and Linux, any GPU (build and start)
Why
On a Mac the game ran out of GPU memory as it loaded the first scene and the device was lost: the GPU's in-use memory climbed to
53 GB of 64 in about 15 s. The cause is how MoltenVK draws 8-bit indices: Metal has none, so before every such draw MoltenVK
widens the indices to 16 bits on the GPU, into a temporary of twice the bound size, and a bind without a size reaches the end of
the buffer. LS binds a guest pool's whole buffer at the indices, so a six-index draw in a 64 MB pool widened 64 MB into a 128 MB
temporary, and each of LS's 48 recording pools keeps every such temporary until the pool is destroyed. This PR binds a direct
draw's 8-bit indices with their own size on MoltenVK, so only those are widened. It is part of the macOS port. See #420.
How to reproduce
Seen on: macOS 26.7.1, Apple M4 Max, MoltenVK 1.4.2
Settings and switches: defaults (the macOS stack without this PR)
Steps: start the game, load the field-dawn save (START, then A), and sample the GPU's memory
(
ioreg -r -c AGXAccelerator -d 1) and the game'sIOAccelerator (graphics)regions (footprint -v)Expected: the GPU's memory stays within a few GB and the load reaches play
Actual: 128 MB
IOAccelerator (graphics)regions pile up (98 at the title, 385 after the A in run #23), the GPU's memoryreaches about 53 GB, IOGPU logs
kIOGPUCommandBufferCallbackErrorOutOfMemoryand the device is lostWhat changed
On MoltenVK's driver alone (vendor fix
index8_size,RX_VK_INDEX8_SIZE), withVK_KHR_maintenance5enabled for it, a directdraw's 8-bit indices are bound with
vkCmdBindIndexBuffer2KHRand their own count: MoltenVK widens exactly the indices the drawreads, at the same point of the command buffer, so what is drawn is the same. Indirect draws keep the bind to the pool's end
(their indices are read where the GPU finds them). Every other driver binds as before.
gpu/vk/vk_vendor.hVendorFixes::index8_size(on forVK_DRIVER_ID_MOLTENVK;RX_VK_INDEX8_SIZE=0/1overrides);gpu/vk/vk_main.cppcreate_deviceasks forVK_KHR_maintenance5only where the fix is on, the device takes 8-bit indicesand has
maintenance5, and says which (vk: 8-bit indices: …);gpu/vk/vk_internal.hDevice::index8_size.gpu/vk/vk_draw.cppindex8_bind_size(a direct 8-bit draw'scountbytes, elseVK_WHOLE_SIZE),bind_indextakes the size and calls
vkCmdBindIndexBuffer2KHRonly for a sized bind, and the bind cache (IndexBind,index_bind_same) is keyed on it;gpu/vk/vk_loader.hloadsvkCmdBindIndexBuffer2KHR;gpu/vk/vk_recorder.hpacks it andgpu/vk/vk_work.hroutes it through the recorder.index8_note/draw_index8_reportcount the 8-bit draws, direct andindirect, the bytes a direct one binds and what their pools hold past the indices (
vk_replay.cpp, beside #677'sreport;
vk_draw.h).docs/development.md, theRX_VK_INDEX8_SIZErow (3e34116c).tests/test_index8_bind.py(new) runsindex8_bind_sizeand the bind on authored draws and checks the gate, the devicesetup and the report;
tests/test_draw_binds.py(the bind cache keyed on size),tests/recorder_sync_test.cpp(the recorder'scoverage of the new call) and #663's
tests/seg_gathers_test.cpp(its fake) follow.Measurements
Verdict: fixed: with this change the game reached play and held it, with no new 128 MB region and the GPU's memory at 9.3 GB
at most, where without it the device was lost at 53 GB during the load. Probe MT-01 confirmed the mechanism and the fix on the
GPU, 22 of 22 steps as predicted.
Baseline: main does not start on macOS. The columns are integration builds, arm64, MoltenVK 1.4.2, the field-dawn save, the
same inputs:
552cc3d4(run #23, the integration branch just before this commit) ande7730869(run #24, the same plus thiscommit; run #25 the same build warm, holding play 900 s).
Hardware: macOS 26.7.1, Apple M4 Max (40-core GPU), MoltenVK 1.4.2, 16-core CPU, 64 GB
Scene: start, title, START and A, the field-dawn save's load, play (#25: 900 s held in play)
Method: the runs' 1-2 s
ioregsamples of the GPU's in-use memory,footprint -vevery 5 s (the 128 MBIOAccelerator (graphics)regions), IOGPU kernel lines (
log stream); one run each (reports/2026-11-14-mac-startup-23.md,-24.md,-25.md). MT-01:reports/MvkTempBuffers-files/mt01/runs-mt01-arm64/(result.json24a7e5f0…),reports/2026-11-14-mvk-temp-buffers.md§6How to reproduce: the runner commands in those reports; for MT-01, its
driver.py runcommand in §6IOAccelerator (graphics)regionskIOGPUCommandBufferCallbackErrorOutOfMemory, device lostvkCmdBindIndexBuffer2KHR, 6 B): the fixFlags and settings
One new switch, a vendor fix's override: on by default on MoltenVK only.
RX_VK_INDEX8_SIZE=0or1VK_KHR_maintenance5)0off,1on where the device hasmaintenance5and 8-bit indicesTesting
Tested: on macOS 26.7.1, Apple M4 Max, at this head (main
6c9edffeplus #677, #663 and what it carries):tests/test_index8_bind.pywith/usr/bin/clang++andclang++ -arch x86_64(the fixture under Rosetta): pass; with the testcopied onto #677's head it fails (
reports/PubWave-files/PubLate2/proof-02a/mt-*,mt-base-index8-*).tests/test_draw_binds.py,tests/test_recorder_sync.py(both compilers),tests/test_seg_gathers.pyandtests/test_mode_census.py(--arch arm64,--arch x86_64): pass (proof-02a/mt-*).gpu/vk/vk_draw.cpp,gpu/vk/vk_main.cppandgpu/vk/vk_replay.cppcompiled whole for arm64 and x86_64 with main's rendererflags (#476's, #492's and #490's macOS compile pieces merged in a scratch tree only): 6 objects, exit 0, no warnings (at
03b2a65e; this head adds onlydocs/development.md)(
reports/PubWave-files/PubLate2/compile/mvk-temp/).unifdef -U__APPLE__): nine files differ (the fix is gated on the driver id, not on__APPLE__); off MoltenVK thefix is off, so every index bind is
vkCmdBindIndexBufferto the buffer's end as before,maintenance5is not asked for and thereport prints nothing (
reports/PubWave-files/PubLate2/offapple-mvk-temp.txt).tools/ls-suite.pyat this head: 208 pass, 16 fail: 13 fail on main6c9edffeon this Mac too, andtest_precompile_compute_guard,test_shader_module_guardandtest_present_aspect_vulkan, which main's full suite skips here and which fail the same way at#663's head when named (
reports/PubWave-files/PubLate2/related-mvk-temp-01/,-compare.txt,related-base-b8579f1a-01/).reports/2026-11-14-integration-2.md).Not tested: a game start on this PR's stack (main does not start on macOS by itself; runs #24/#25 had this commit unchanged);
indirect 8-bit draws (still bound to the pool's end: none in #25/#26);
RX_VK_INDEX8_SIZE=1on another driver; not built onWindows or Linux; its test request covers it.
Must be tested:
vk: 8-bit indices: … (VK_KHR_maintenance5): yes, no growing count of 128 MBIOAccelerator (graphics)regions and no deviceloss (by hand: the parent's game run).
3e34116c, it carries #677, #663, #662, #658, #649, #648, #647, #645,#644, #643 and #491) and main
6c9edffethe same way and start each to the title, expecting novk: 8-bit indicesline and everyother line to match main's (by hand: test request T-XXXX).
Risks
What could break: on MoltenVK only: a direct 8-bit draw whose indices run past
countbytes from the bound offset would readpast its bind (draw() records firstIndex 0, so the draw reads exactly
countindices); a MoltenVK withoutmaintenance5keeps theold bind (the start-up line says so). Indirect 8-bit draws still widen to the pool's end.
Turning it off:
RX_VK_INDEX8_SIZE=0, or revert the PR.Compatibility: Nothing changes for players elsewhere; on a Mac the device enables one more extension. No file in the shader
stamp changed; no
MKWVK_API_VERSIONchange.Reviewer notes
e1153ec7..3e34116c(2 commits):cherry-pick -xofmacos/mvk-temp0fdc1cc8(03b2a65e), with two conflicts wherethe integration branch's neighbours are not here:
vk_draw.h(abovedraw_layouts_report's comment as #663 has it) andvk_vendor.h(nocompiler_service, #650's); the pick's changed lines equal the source commit's (sorted;pick-mvk-temp-lines.txt). Then3e34116c, the switch's row (the topic had none).log_frame_stats, andtest_index8_bindfinds it there) and throughit #663 (
seg_gathers_test.cpp's fake), #662, #658, #649, #648, #647, #645, #644, #643 and #491.git merge-treeof this head (reports/PubWave-files/PubLate2/merge-check-mvk-temp.txt):gpu/vk/vk_draw.cppwith#681 (inherited from #677);
gpu/vk/vk_draw.hwith #646 (inherited);vk_vendor.hand the rest with#650/#652 and its stack (inherited from #663). With #679 and #680 (also on #677): clean; read
together, an 8-bit count draw rewritten on MoltenVK reaches the indirect branch and keeps the pool's end, and both reports count
it (Integration 34).
Issues
See #420
Checklist
Everyone
type(scope): description) of the status line's type.main(maine090cc48).python -I -B tests/run_all.pypasses (any failure that also fails onmainis named). (On the wave's merge937a502a= this PR3e34116c+ drawid-direct9c2bd272(carries count-draws and mode-census, which this PR is on) + metal-scratch4edae82c: 562 passed, 31 failed, 18 skipped against main 6c9edffe's 531/32/17 on this Mac; the 31 failures are main's own and nothing that passes on main fails;test_collect_widenow passes; 30 new tests pass;test_darwin_audio_service, Darwin-only, is skipped by the runner;reports/PubWave-files/waveC2r/full-937a502a/.)third_party/untouched (a new folder with aPROVENANCE.mdinstead).When it applies
Assisted-by:/Co-Authored-By:trailers.mainand passing here.tests/that reads changed source updated in this PR, not weakened.Every scan down vk_memory.cpp's import table by start (pool_lookup's covering import and merge plan, bg_drain, prefetch_chunks, import_in_background, memory_note_gpu_write and memory_guest_imported) stopped once an import ended more than 1 GiB below its address, on the belief that no import is larger than that. pool_lookup's own merge escape leaves an import above 1 GiB over the smaller ones inside it ("left overlapping"), and the device allows imports up to max_import_size: a scan stopped at a small import inside a large one, missed the large one, and the same bytes were imported again, two memories over the same bytes. import_reach.h counts the live imports by span class; its bound is above every live span, within twice the largest. imported_add and imported_take, now the table's only ways in and out, keep the count. A scan stops only where no import further down can reach its address, so it also stops sooner than before when the imports are small. The covering-import checks in pool_lookup and import_in_background look past the last import at or below the range for the same reason. Tests: test_import_reach.py runs the actual scans with a 4 GiB import over a 16 MiB chunk, left by the merge escape (imports are recorded ranges: no payload, no Vulkan, no game). Its lookup, query, note, drain, background and prefetch cases fail on main5e072fc8and pass here, and a source check keeps every change to the table in the two helpers. test_import_windows runs pool_lookup with the helpers; test_mirror_gpu_only names the new publication point. Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]>044635ea added vma_startup_rollback (vk_vma.cpp, run after a failed replay_start), which calls vmaDestroyAllocator. vk_vma.cpp includes vk_work.h last so that RX_VK_RECORDER=defer/thread drains before its destructions, and every such boundary call in a vk_work.h file must be in RX_REC_BOUNDARIES with a drain-first macro. This one was not, and test_recorder_sync caught it ("vk_vma.cpp calls ['vmaDestroyAllocator'], which vk_work.h does not drain before"): it passes at 58c5c5aa (044635ea's parent) and fails at 044635ea. Add it to the list and to vk_work.h, next to vmaDestroyBuffer and vmaDestroyImage. With the recorder off (the default) boundary() is a relaxed load and a branch. Rollback runs before any image or buffer exists, so nothing should be held there today, but the allocator is no longer destroyed while a recorder could still hold packets. The test is unchanged (sources: 42 boundaries drained, was 41). Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]>A guest span larger than one device allocation (the cap on MoltenVK/M4 Max is 41,747,087,360 bytes) is bound as pieces: one descriptor per allocation segment, at the descriptor's own binding (reports/2026-11-14-full-range-design.md sections 4.1-4.4). This is the shader half; the draw side (descriptors, layout, gathers) comes later. - runtime_info.h: SegEntry {Storage|Table|TexBuf|ImgBuf, desc, pieces} and RuntimeInfo::segmented. - Back end: a segmented storage buffer is an array of pieces at its binding (a table count * pieces, entry k's piece j at k * pieces + j); its loads, stores and atomics call DontInline helpers made after main, which find the piece by the pieces' OpArrayLength in order, with constant indices. The global memory fallbacks sum the pieces' lengths for a segmented descriptor's bound end and branch to its piece (single, native candidate, table written out and in the loop). Texel and image buffers are arrays too, their fetches, reads, writes and atomics through helpers that pick the piece by OpImageQuerySize, and a texel buffer's size query sums the pieces. ImageQuery was declared for every module already. With RuntimeInfo::segmented empty nothing new is made: the SPIR-V is byte-identical. - vk_shader: SegSig (entries, hash) on Program, seg_sig and seg_variant; program_segmented finds or translates the variant of a plain program with plain's texture questions and answers and checks its descriptors are plain's; program_pick, mesh_program_locked, program_find_plain, loaded_variants and portable_variant keep the plain and segmented variants apart; every stage's RuntimeInfo::segmented comes from Program::seg. - vk_progcache: a segmented variant is never written to the program cache nor listed among the loaded programs. - tests/test_seg_shader.py + tests/seg_shader_ir.cpp: synthetic IR programs through the real back end, plain and segmented; structure checks, spirv-val (Vulkan 1.3, uniform buffer standard layout), and with --base-tree a byte comparison of the plain modules against an older tree. Five source-reading checks follow the new Program field and the atomics' new branch. The translator stamp changes with this (eden/, vk_shader.cpp, sizeof(Program)): every program cache is rebuilt once. Land it in the same release as the vk_api.h change that already does so. Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]> (cherry picked from commit b7928876dab846485f667c1c934d34d25ecef035)The interfaces the four segmented-consumer lanes (SegBind, SegXfer, TexelDesc, NullShader; reports/2026-11-14-seg-consumer-plan.md section 3) code against, frozen before they fork. Inert: no caller of anything new, no SPIR-V, layout, push range or stream change, sizeof(Program) unchanged. - vk_internal.h / vk_memory.cpp, SegMem's consumer interface: gpu_span_any() (a relaxed count of the live domains, stored in seg_commit; domains are kept for the run), gpu_span (gpu_buffer's flavour of gpu_span_bind: import buffers, no written marks, no mirror), SpanLayout::bind_stamp (gpu_bind_stamp(): a segment can be imported again with its cuts kept, so cut_gen alone never keys piece buffers), span_unused_piece's semantics ({null_storage, 0, 1}), and the SegArena API (SegArenaRef, seg_arena_take, seg_gather, seg_scatter; stub bodies after stream_alloc that give no room and log, SegBind's to fill). - Review fixes in the same interface (renderer-core review P2-3, P3.2): every piece of gpu_span_bind carries its buffer's device address (the import's or the mirror's; 0 only with bufferDeviceAddress off), and its one-piece path stores the translated guest address, not a virtual one. - vk_texture.h/.cpp: texel_view_pieces / texel_piece_views, stubs that return 1 and false (TexelDesc's to fill). - vk_shader.h: Program::presence_words, in what was padding. - Back end: PRESENCE_PUSH_OFFSET (88), Profile::emulate_null_descriptors, Bindings::presence / presence_read with the bit numbering rule. - tests: test_resolver_coverage lists gpu_span_bind / gpu_span sites too (scoped to gpu/vk: gpu/render has an rx::gpu_span of its own), checks that gpu_span follows its own gpu_buffer, and splits SITES into SITES_BASE plus one block per lane. test_segmented_domains executes the contract (the count 0, 1, 2 -> 1 on a merge, 0; gpu_span's pieces; addresses with the fixture's gpu_buffer_bind returning none as the real one does; the bind stamp; a virtual address's guest). test_seg_shader accepts a base tree of this back end's generation and compares every module. - docs/segmented-binding.md: the gate (every new behaviour Apple-only, other platforms byte-identical) and one heading per lane. Conflict on this branch (not with main): tests/test_seg_shader.py's docstring, against the array_pointer_calls paragraph #P20's msl-arrayptr port added; both kept, this paragraph first. Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]> (cherry picked from commit 95fa06d4e6526601bd2e1bc88c2f8f5720855350)The segmented single storage array's case (plan 4.3 item 5) had no negative: the check always cut its own tree. With --source <B2 archive> it fails as required ("moltenvk.segmented_single want=set got=push"). Conflict with #P28 (read_write textures; not with main): the docstring keeps #P28's paragraph with this usage line, and main() cuts from --source's vk_draw.cpp with #P28's read_write count (as in the macOS integration, Integration 17). Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]> (cherry picked from commit 5824f6828e21cf810dcceaa6be425a9224b15994)plaine37c097da2plaina997b3629aKosmicKrisp has no fillModeNonSolid and MoltenVK no POINT polygons, and Metal restarts an indexed strip or fan at the all-ones index whatever Vulkan's restart enable says. Before anything is fixed, count whether the game needs it (mode_census.h, Apple only; nothing built or drawn changes): - the graphics pipelines built, where st_pipelines counts them, and the draws recorded, where st_draws counts them, by NVN's polygon mode, with the first 8 LINE and POINT pipelines (program, pipeline key, topology) and programs named; - the indexed strip and fan draws with restart off; a direct one's indices are read whole, a page at a time, through memory_read_as_submitted for the index type's all-ones value (0xFF, 0xFFFF, 0xFFFFFFFF). An indirect one's range is the GPU's and a range the CPU cannot read is not guessed: both are counted as not scanned. Any other draw costs restart_off_strip's compares and its polygon mode's count on the thread's own counters. Printed with the frame statistics every 120 presents ("at present N") and at close ("at close"). The two tests that compile build_graphics and draw()'s binds from the source get a stand-in for the counts. Assisted-by: Claude Opus 5.5 Co-Authored-By: Claude Opus 5.5 <[email protected]> (cherry picked from commit 1bd30dceb348909ca03c4cf12709dccbb0900f4a)3e34116ccb76cdd7a70376cdd7a703989a6423d9Folded into #850 (fix(macos): draw-path emulation on MoltenVK)
Pull request closed