19056282b6
Target: Reduce wrapper_env_cfg() overhead in malloc/free hot path - Strategy: Cache wrapper env configuration pointer in TLS - Approach: Fast pointer cache (TLS caches const wrapper_env_cfg_t*) Implementation: - core/box/wrapper_env_cache_env_box.h: ENV gate (HAKMEM_WRAP_ENV_CACHE) - core/box/wrapper_env_cache_box.h: TLS cache layer (wrapper_env_cfg_fast) - core/box/hak_wrappers.inc.h: Integration into malloc/free hot paths - ENV gate: HAKMEM_WRAP_ENV_CACHE=0/1 (default OFF) A/B Test Results (Mixed, 10-run, 20M iters): - Baseline (D2=0): 46.52M ops/s (avg), 46.47M ops/s (median) - Optimized (D2=1): 45.85M ops/s (avg), 45.98M ops/s (median) - Improvement: avg -1.44%, median -1.05% (DECISION: NO-GO) Analysis: - Regression cause: TLS cache adds overhead (branch + TLS access) - wrapper_env_cfg() is already minimal (pointer return after simple check) - Adding TLS caching layer makes it worse, not better - Branch prediction penalty outweighs any potential savings Cumulative Phase 2-3: - B3: +2.89%, B4: +1.47%, C3: +2.20% - D1: +1.06% (opt-in), D2: -1.44% (NO-GO) - Total: ~7.2% (excluding D2) Decision: FREEZE as research box (default OFF, regression confirmed) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
26 lines
1.1 KiB
C
26 lines
1.1 KiB
C
// wrapper_env_cache_box.h - TLS cache layer for wrapper env config (Phase 3 D2)
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// Purpose: Eliminate repeated wrapper_env_cfg() calls in malloc/free hot path
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// Strategy: Cache the const pointer in TLS (safe, no refresh sync needed)
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#pragma once
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#include "wrapper_env_box.h" // wrapper_env_cfg()
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#include "wrapper_env_cache_env_box.h" // wrap_env_cache_enabled()
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// Fast pointer cache: TLS caches the pointer to g_wrapper_env
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// Safety: wrapper_env_refresh_from_env() doesn't change the pointer address,
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// only the content of g_wrapper_env, so TLS cache remains valid.
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static inline const wrapper_env_cfg_t* wrapper_env_cfg_fast(void) {
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if (__builtin_expect(!wrap_env_cache_enabled(), 1)) {
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// Cache disabled (default): use baseline wrapper_env_cfg()
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return wrapper_env_cfg();
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}
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// Cache enabled: TLS fast pointer
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static __thread const wrapper_env_cfg_t* cached_ptr = NULL;
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if (__builtin_expect(cached_ptr == NULL, 0)) {
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// First access: initialize TLS cache with pointer to g_wrapper_env
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cached_ptr = wrapper_env_cfg();
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}
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return cached_ptr;
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}
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