Refactor feature extractors to match production instruction mix (#705) - #705
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…bookresearch#705) Summary: Pull Request resolved: facebookresearch#705 Replace scalar FP transforms with integer hash operations, add data-dependent conditional branches, eliminate FP division with integer reciprocal approximation, deepen MockHashTable::find() call chain from 1 to 5 levels, and increase basic block sizes with MurmurHash-style computation chains. Results (5/7 instruction mix targets met on CPL): - Scalar FP: 8% → 0.46% (target <3.5%) ✓ - Conditional branches: 5.28% → 10.73% (target >15%) ✗ - Near call/return: 3.93% → 0.75% (target <1.5%) ✓ - Memory (ld+st): 51.56% → 40.72% (target 40-46%) ✓ - Divider active: 11.50% → 1.13% (target <2%) ✓ - Avg BB size: 7.3 → 13.7 (LBR, target >18) ✗ QPS impact: CPL -2.2%, BGM -6.3%, Grace -3.8%. Reviewed By: charles-typ Differential Revision: D99494831
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Summary: Add mock feature extraction pipeline to FeedSim with large-scale code generation for I-cache and frontend pressure. 27 genuinely diverse code patterns (derived from studying 696 production feature extractors) generate ~700 variants × 1000 copies = ~700K unique functions at install time. Key components: - 6 hand-written extractors based on production leaf function profiling - 27 pattern-specific code generators (P01-P27) producing genuinely different instruction sequences (different branch topologies, loop nesting, data access patterns, code sizes from 10 to 2300 lines) - Flat shuffled dispatch: all copy function pointers shuffled into one vector, iterated sequentially per request for maximum I-cache pressure - DLRM medium/large model generation on-server during install - Configurable via --num_stories, --extractors_per_story, --feature_complexity Results on T1_BGM (Bergamo, 176 cores): 500K calls/req: L1 I-Cache MPKI 21.34 (prod target 21), IPC 0.69 (prod 0.6-0.8) 100K calls/req: Frontend Bound 23.5%, IPC 1.22, QPS 242 Results on T11_GRC_ARM (Grace, 72 cores): 100K calls/req: IPC 0.52, L1 I-Cache MPKI 15.91 Medium DLRM + 100K calls: IPC 1.03 (prod target 1.05) Differential Revision: D97022149
…bookresearch#705) Summary: Pull Request resolved: facebookresearch#705 Replace scalar FP transforms with integer hash operations, add data-dependent conditional branches, eliminate FP division with integer reciprocal approximation, deepen MockHashTable::find() call chain from 1 to 5 levels, and increase basic block sizes with MurmurHash-style computation chains. Results (5/7 instruction mix targets met on CPL): - Scalar FP: 8% → 0.46% (target <3.5%) ✓ - Conditional branches: 5.28% → 10.73% (target >15%) ✗ - Near call/return: 3.93% → 0.75% (target <1.5%) ✓ - Memory (ld+st): 51.56% → 40.72% (target 40-46%) ✓ - Divider active: 11.50% → 1.13% (target <2%) ✓ - Avg BB size: 7.3 → 13.7 (LBR, target >18) ✗ QPS impact: CPL -2.2%, BGM -6.3%, Grace -3.8%. Reviewed By: charles-typ Differential Revision: D99494831
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Summary: Pull Request resolved: #705 Replace scalar FP transforms with integer hash operations, add data-dependent conditional branches, eliminate FP division with integer reciprocal approximation, deepen MockHashTable::find() call chain from 1 to 5 levels, and increase basic block sizes with MurmurHash-style computation chains. Results (5/7 instruction mix targets met on CPL): - Scalar FP: 8% → 0.46% (target <3.5%) ✓ - Conditional branches: 5.28% → 10.73% (target >15%) ✗ - Near call/return: 3.93% → 0.75% (target <1.5%) ✓ - Memory (ld+st): 51.56% → 40.72% (target 40-46%) ✓ - Divider active: 11.50% → 1.13% (target <2%) ✓ - Avg BB size: 7.3 → 13.7 (LBR, target >18) ✗ QPS impact: CPL -2.2%, BGM -6.3%, Grace -3.8%. Reviewed By: charles-typ Differential Revision: D99494831 fbshipit-source-id: dba6926afe8c0dfb4efed7a0006cfcf62b2268b1
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Summary:
Replace scalar FP transforms with integer hash operations, add data-dependent
conditional branches, eliminate FP division with integer reciprocal approximation,
deepen MockHashTable::find() call chain from 1 to 5 levels, and increase basic
block sizes with MurmurHash-style computation chains.
Results (5/7 instruction mix targets met on CPL):
QPS impact: CPL -2.2%, BGM -6.3%, Grace -3.8%.
Reviewed By: charles-typ
Differential Revision: D99494831