[Yasei-no-otoko]

Strata's CPU pinning lost part of the processor identity on Windows and part of the caller's saved CPU mask on Linux. Windows workers discarded the processor-group number; Linux host restoration retained only CPU IDs 0-63. This change preserves the full placement on both platforms without changing automatic worker sizing or explicit --pool-workers values.

On Windows, use SetThreadGroupAffinity for pool-owned workers, enumerate every core group mask and preserve group identity in fallback enumeration. On the tested 3990X, the previous 63-worker list collapsed to 32 distinct group-local masks because SetThreadAffinityMask(..., 1 << (core & 63)) discarded the group.

The caller-owned Windows host thread uses reversible CPU Set selection. Save its full explicit selection and restore it, or clear it when originally empty. This preserves process-default inheritance and Windows 11's implicit all-group eligibility without changing existing hard affinity. CPU Sets are soft placement constraints. See Microsoft's CPU Set API.

On Linux, retain the complete native affinity mask in ThreadAffinity. Use CPU_ALLOC and the sized CPU-set macros, retry a query with a larger buffer on EINVAL, and share the dynamic-mask handling with topology enumeration and worker pinning. Restore the complete saved mask, including high-only and sparse selections, and report failed affinity operations using pthread's returned error number. See Linux CPU-set APIs. No Windows-style group IDs are needed on Linux.

Validation:

• Windows 11 Pro 10.0.26300 / Threadripper 3990X: rebuilt the Windows pool_affinity_test after the Linux addition; CTest passed. It covers worker pins, reversible host selections, process defaults, and continued execution in both processor groups. The earlier Windows change also completed a full Release HIP engine build; details are in bench: report Coder IQ1_M on Threadripper 3990X and RX 6900 XT #628.
• Ubuntu 24.04 under WSL 2, GCC 13.3: built strata_kernels_cpu and pool_affinity_test with GPU/native-ggml support disabled. -Wall -Wextra -Werror syntax checks passed for the changed Linux implementation and test. CTest passed with 64 available CPUs, and a separate run with taskset -c 0,2,15 passed. The high-CPU path correctly reports a skip on these WSL runs.
• A diskless QEMU TCG guest using Linux 6.6.36.3-microsoft-standard-WSL2 exposed CPUs 0-127. The same statically linked regression test passed with --require-high-cpu, both with all 128 CPUs and with affinity restricted to CPUs 64-127. Tests include full-mask and sparse/nested restoration, a high-only saved mask, topology respecting the allowed CPU set, worker execution on CPU 127, invalid targets, and cleanup.
• A separate negative-control binary deliberately truncated the saved Linux mask to one 64-bit word. Both QEMU scenarios failed as expected: the full mask restored only 64 of 128 CPUs, and the high-only scenario retained just the pinned CPU after restoration failed. The injected control is not part of the committed source.

Linux reproduction on a normal Linux checkout:

cmake -S . -B build-affinity -DSTRATA_BUILD_TESTS=ON \
  -DSTRATA_NATIVE_EXPERTS=OFF -DSTRATA_ENABLE_CUDA=OFF -DSTRATA_ENABLE_HIP=OFF
cmake --build build-affinity --target pool_affinity_test --parallel 4
ctest --test-dir build-affinity -R '^pool_affinity_test$' --output-on-failure -V
# Requires at least two allowed CPUs, including an ID >= 64:
./build-affinity/pool_affinity_test --require-high-cpu

The Linux results establish affinity correctness in WSL / an emulated guest, not native Linux inference performance. CPU IDs above 1023 were not exercised. The AVX-512 pool self-test and pool_stress skip their workloads on this 3990X; a zero exit code from those skips is not a stress-workload pass.

Benchmark data remains in the separate PR #628. Its speed figures belong to the recorded earlier Windows revisions and predate both the Windows host CPU Set review follow-up and this Linux addition; inference throughput was not remeasured for this revision. The machine's one NUMA node spans two processor groups, so this is an application affinity correction, not a Windows Containers or OS NUMA fix.

[Copilot]

Copilot review overview

🟡 Changes recommended

Windows 11’s implicit all-group affinity cannot be restored from the saved primary group and mask.

Review effort: Balanced
Findings: 1

Open (1)

• Thread teardown fails to restore unpinned all-group affinity · New

What changed in this PR

Updates Windows CPU affinity handling to preserve processor-group identities during worker and host pinning.

Changes:

• Adds group-aware topology discovery and thread pinning.
• Introduces structured affinity state and restoration.
• Adds a Windows pin/restore integration test.

File	Description
src/​kernels/​cpu/​pool.cpp	Implements group-aware topology, pinning, and restoration.
src/​kernels/​cpu/​pool_affinity_win.hpp	Adds the shared Windows affinity helper.
src/​kernels/​cpu/​pool_affinity_test.cpp	Tests Windows group pinning and restoration.
src/​core/​session.cpp	Tracks whether host pinning succeeded.
include/​strata/​kernels/​cpu/​pool.hpp	Defines structured affinity state.
include/​strata/​core/​session.hpp	Stores the new affinity state type.
CMakeLists.txt	Registers the Windows affinity test.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The implementation preserves processor groups and caller affinity state with focused regression coverage.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Thread teardown fails to restore unpinned all-group affinity

[Niko1221]

Thanks! Taken into 0.1.39, the net diff squashed into one commit. pool_affinity_test passes here (one processor group). On our 6-core Ryzen, 10 interleaved decode pairs were within noise on Q2_0 and IQ3_XXS with the host on CPU Sets. The >64-CPU behavior is your 3990X and QEMU testing.