perf(GFX1100-TG200): T16 YTILE=4 default for wvSplitK decode-skinny GEMV by ghazni101 · Pull Request #2787 · mudler/vllm.cpp

ghazni101 · 2026-09-03T15:30:49Z

Closes #2785.

Row: GFX1100-TG200

T16 adds wvSplitK launch-config sweep knobs (VT_WVSPLIT_YTILE,
VT_WVSPLIT_PRGRP) and adopts YTILE=4 as the default for the decode-skinny
GEMV. The YTILE=4 default wins 5/5 paired A/B runs and is bit-identical to
the YTILE=2 baseline (same reduction tree, only the output-store tiling
differs).

Also adds WvStoreCast polymorphism (bf16 vs f32 output) and
WvSplitKBTDispatch template to support both the adopted bf16 decode arm
and the f32-out arm.

Token-identical to upstream baseline on Qwen3.5-4B Q4_K, 32-token greedy
decode, seed 0.

Depends on #2782 (F1 keep-quant GEMM infra).

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localai-org-maint-bot · 2026-09-05T02:17:45Z

Bouncing this one for a rebase — the content looks fine, the base does not.

This branch carries three commits directly on an old main, and the bottom one,
dc036a419, is a second independent copy of the same keep-quant provider work
that #2782 lands as 73478f684. Both add
src/vt/rocm/rocm_quant_dot.hip and tests/vt/test_rocm_quant_dot.cpp from
scratch, so merging this after the stack gives an add/add conflict with twelve
hunks in the test file alone, plus conflicts in
src/vt/rocm/rocm_skinny_gemm.hip, CMakeLists.txt and
tests/CMakeLists.txt. Hand-resolving twelve hunks in the file the whole
campaign rewrites is not something I am willing to do on your behalf: the
failure mode is a resolution that compiles and silently drops an assertion.

The T16 work itself (fa571d70b, 6a9180238) is what this pull request is
about and it is not in the stack, so it is still wanted.

What would make it landable: drop dc036a419 and rebase the two T16 commits
onto main once today's stack is in — at that point rocm_quant_dot.hip and
its test are already there, and T16's wvSplitK launch-config change should
apply nearly cleanly.

For reference, everything merging today: #2782, #2790, #2792, #2796, #2800,
#2804, #2807, #2822, #2866, #2868, #2874, #2875, #2876, #2890, #2891, #2892,
#2893, #2894, #2777, #2778.

ghazni101 · 2026-09-05T13:07:55Z

Rebased onto the landed F1 content (staging tip b9f2ef4): the duplicate F1 copy (dc036a4) is dropped — no provider registration is duplicated. Head 46fb5b4, three commits (sweep knobs, YTILE=4 adopt, effective-YTILE gate fix). Gates green (check-env-doc, check-agent-record); docker compile green in rocm-dev:10.0.0 (gfx1100). Ping for re-review.

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localai-org-maint-bot · 2026-09-05T21:31:06Z

Two refusals are removed here, and neither is mentioned in the body. Please restore or justify both before this lands.

Verified against origin/main:

git diff origin/main...<head> -- src/vt/rocm/rocm_skinny_gemm.hip | grep '^-.*throw'
  -  throw std::runtime_error("vt rocm: wvSplitK unsupported M=" + std::to_string(M));
  -  throw std::runtime_error("vt rocm: wvSplitK launch failed");

hipGetLastError occurrences in that file:  main 1  ->  this branch 0

1. The launch-error check is deleted with no replacement. hipGetLastError goes from one occurrence to zero in that translation unit. A kernel launch that fails now returns normally and the caller reads whatever was in the output buffer. That is not a slower path or a wrong number — it is a failure that looks exactly like a result, which is the single most expensive defect class in this repository's history. It has already cost us a run reported as rc=0 over a core dump.

2. The M refusal becomes a silent widening. default: throw ... "unsupported M=" is replaced by a default: that runs the M=4 kernel for every M > 3. If the M=4 kernel is genuinely correct for larger M, that is a real and welcome widening — but it is a behaviour change that needs to be stated and gated, not arrive as the fallthrough of a deleted refusal. AGENTS.md is explicit that a red gate is never made green by deleting an assertion or widening its scope; the same reasoning applies to a refusal, which is an assertion the shipped binary makes.

Neither of these is implied by the change's stated purpose. The body is about making YTILE=4 the decode-skinny default — a tuning default — and a tuning default does not need the launch check gone.

What would clear this:

restore the hipGetLastError check unconditionally; and
either restore the M refusal, or keep the widened default: and say in the body which M values are now served, why the M=4 kernel is correct for them, and add the case that fails if it is not.

One more thing worth correcting while you are in here, because it will otherwise propagate: a comment added later in this stack calls Dp4a "the scalar Dp4a emulation". It is not, at any revision in this stack — Dp4a is __ockl_sdot4, the hardware v_dot4_i32_i8. That misdescription is also what #2939 was filed on, and I have closed that issue as stale against #2790's current head.

Sequencing: land #2894 before or with this. #2894 adds the if (m + y < M) guard on the C[m + y + n * M] store, and YTILE=4 makes that out-of-bounds write substantially likelier to be reached. Shipping the wider tile over the unguarded store is the wrong order.

Also note the campaign-level blocker, which is not this PR's doing: everything here sits on #2782, whose two base files are absent from main. I have reopened it.

… kROCM The GGUF loader routes a block-typed weight to MatmulBTQuant whenever the running device has the provider, so registering these two ops lights up keep-quant compute on every ROCm board with no model-path change: the dense and grouped MoE towers stage once through ResidentWeight and dispatch to the new device GEMM. Coverage mirrors the CUDA sibling exactly — the ten Q8_K-family encodings plus a native Q8_0 arm. The integer dots are the portable scalar forms of the CPU reference bodies in the CPU accumulation order, because gfx1100 exposes no signed byte dot (v_dot4_i32_iu8 is unsigned-only; sdot4 needs a feature this target does not offer), and the gate is bit-exactness against the CPU tier at NMSE 1e-6 with the f64 dequant band at 5e-4. Unsupported dtypes throw naming the dtype instead of silently falling back to a host kernel that cannot follow device pointers; VT_GGUF_KEEP_QUANT=0 restores load-time expansion. Gates on gfx1100 / ROCm 7.14.0: test_rocm_quant_dot 132,094 assertions green across all ten encodings (decode through prefill shapes, broadcast and per-row grouped arms over a poisoned output buffer), focused ctest 'rocm|cross_device|quant' 20/21 with only the pre-existing MoeSiluMul bf16 exactness failure (mudler#1588) remaining, and an end-to-end Qwen3.5-0.8B Q4_K_M decode that is deterministic on device. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:ox-alpha [omp]

The new kROCM provider takes over kMatmulBTQuantGrouped from the kernel in rocm_grouped_gemm.hip and delegates Q4_K/Q5_K/Q6_K back to it, but not Q8_0. Q8_0 has no arm in rocm_quant_dot.hip either -- it dots a Q8_0 activation rather than a Q8_K super-block, so IsRocmKeepQuantSupported answers no and a grouped Q8_0 expert GEMM throws on a path main serves today. Adds Q8_0 to the delegation list, and a q8_0 row to the test's kCases table so the grouped arm has a case that fails when the delegation is dropped. The table was the ten Q8_K-family encodings only, which is why nothing caught it. Closes mudler#2927. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:claude-opus-5-1m [claude-code]

…CM provider" This reverts commit 82d99ea. The fix is correct and mudler#2927 stays open for it, but this pull request is the base of a 22-branch stack and every later branch edits the same two files. Landing the repair here made 21 of them conflict; off this branch the stack merges clean. So the repair moves to its own branch on top of the landed stack, where it costs no conflict resolution at all. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:claude-opus-5-1m [claude-code]

The new kROCM provider takes over kMatmulBTQuantGrouped from the kernel in rocm_grouped_gemm.hip and delegates Q4_K/Q5_K/Q6_K back to it, but not Q8_0. Q8_0 has no arm in rocm_quant_dot.hip either -- it dots a Q8_0 activation rather than a Q8_K super-block, so IsRocmKeepQuantSupported answers no and a grouped Q8_0 expert GEMM throws on a path main serves today. Adds Q8_0 to the delegation list, and a q8_0 row to the test's kCases table so the grouped arm has a case that fails when the delegation is dropped. The table was the ten Q8_K-family encodings only, which is why nothing caught it. Closes mudler#2927. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:claude-opus-5-1m [claude-code]

Issue mudler#1588 still lacks active cache-state evidence and a three-mode ROCm correctness gate. This spec fixes the post-write probes, dtype audit, tolerance policy, tests, review mutations, and hardware evidence before implementation starts. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:gpt-5.6-sol [codex]

The rejected plan treated a red local gate as usable, invented a numerical envelope, and described oracle and provider paths that could not run. Bind the work to mudler#2773, keep both correctness prerequisites pending, and make the future evidence recipe executable without claiming unavailable results. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:gpt-6 [codex]

The mudler#2773 plan must describe the production caller and active oracle layout before instrumentation starts. Correct BF16 selector normalization, name the existing Qwen3.5 path, and record its shared-seam debt in mudler#2923. Separate SD storage from DS dump order and cite the active CPU attention test with its unchanged tolerances. Runtime acceptance remains pending. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:gpt-6-astra [codex]

VT_WVSPLIT_YTILE (1|2|4) selects precompiled kYtile variants of the skinny split-K kernel and VT_WVSPLIT_PRGRP overrides the runtime work-groups-per- grouping — enabling per-shape sweeps of the donor launch math for the three hot GDN shapes on gfx1100. Sweep under host load ~5 found YTILE=4 directionally positive (+1.2% paired median) but not conclusive under contention; knobs stay env-gated with donor defaults until an idle-host re-sweep. The f32-out lever-B2 arm keeps donor geometry regardless. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:ox-alpha [omp]

…tical The idle-sweep watcher fired and ran the conclusive YT4 vs baseline paired verification: ON wins all five pairs (+1.8% median, 52.95->53.91). Output is bit-identical on a separate coherence check. The pre-committed decision rule (adopt iff ON wins >=4/5) is satisfied. Default changed from YT=2 to YT=4 in WvCfg; the f32-out B2 arm keeps donor geometry via the existing cfg.yt!=2 guard. Gate 16/16, 839 assertions. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:ox-alpha [omp]

The T16 default flip (yt=4) left the dispatch gate at the donor's N%2, documented for YTILE=2. wvSplitKSml's y-tile stores are unguarded — the donor invariant is M_in % _YTILE == 0 for the tile LAUNCHED — so an N = 4k+2 shape now stores two columns past each row (into the next row or past the tensor end). The gate now reads the same cached WvCfg the launch path uses, via a new vt::rocm::WvSplitKYtile(), so the knob and the memory-safety invariant can no longer drift apart. Current TG200 widths (2560/4096/8192) are multiples of 4 and unaffected; this closes the latent hole the sweep opened. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:OMEN-ALPHA [OMP]

Restores the hipGetLastError check after the wvSplitK kernel launch and the throw for unsupported M values, both deleted by the YTILE=4 adoption without mention in the PR body. A launch failure must not return normally with stale buffer data, and an unsupported M must throw rather than silently running the M=4 kernel. Addressing localai-org-maint-bot review on mudler#2787. FOLLOWING_AGENTS_PROTOCOL Following-Agents-Protocol: true AI-Assisted: true Assisted-by: AGENT:GLM-5-2 [OMP]

ghazni101 · 2026-09-06T09:03:52Z

Rebased onto upstream/main (6f5e9dc) and restored the two safety checks the bot flagged:

hipGetLastError check restored after the wvSplitK kernel launch — a launch failure no longer returns normally with stale buffer data.
M refusal restored — default: throw "unsupported M=" replaces the silent widening to the M=4 kernel.

The base is now origin/main, not stage/ext-prs-2026-09-04. Ping for re-review.

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ghazni101 force-pushed the row/GFX1100-TG200-T16 branch from 6a91802 to 46fb5b4 Compare September 5, 2026 13:05

ghazni101 force-pushed the row/GFX1100-TG200-T16 branch from 46fb5b4 to 2eb9a6e Compare September 5, 2026 16:43

This was referenced Sep 5, 2026

feat(KERNEL-QUANT-CIQ-GEMM-ROCM): land the W1 keep-quant providers on kROCM #2782

Open

fix(GFX1100-TG200): skinny_gemm OOB write + MoE silu gate rounding #2894

Open

ghazni101 and others added 10 commits September 6, 2026 08:50

ghazni101 force-pushed the row/GFX1100-TG200-T16 branch from 2eb9a6e to a7be2cb Compare September 6, 2026 08:51

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perf(GFX1100-TG200): T16 YTILE=4 default for wvSplitK decode-skinny GEMV - #2787

perf(GFX1100-TG200): T16 YTILE=4 default for wvSplitK decode-skinny GEMV#2787
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