fix: use physical cores for --threads auto-detect (#19110) #19260
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Replace std::thread::hardware_concurrency() with cpu_get_num_math() when --threads is set to -1 or 0 (auto-detect mode). hardware_concurrency() returns logical cores (includes hyperthreads), causing thread oversubscription and performance degradation: - 100% CPU usage instead of optimal ~50% - 3.6x slower (2.5 tok/s vs 9 tok/s reported) cpu_get_num_math() returns physical cores and also handles Intel hybrid CPUs by skipping efficiency cores for math workloads. Fixes ggml-org#19110
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This PR changes 4 lines in CPU thread detection logic. The failing jobs are unrelated to the code path modified. |
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Replace std::thread::hardware_concurrency() with cpu_get_num_math() when --threads is set to -1 or 0 (auto-detect mode).
hardware_concurrency() returns logical cores (includes hyperthreads), causing thread oversubscription and performance degradation:
cpu_get_num_math() returns physical cores and also handles Intel hybrid CPUs by skipping efficiency cores for math workloads.
Fixes #19110
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