Phase 86: Free Path Legacy Mask (NO-GO, +0.25%)
## Summary Implemented Phase 86 "mask-only commit" optimization for free path: - Bitset mask (0x7f for C0-C6) to identify LEGACY classes - Direct call to tiny_legacy_fallback_free_base_with_env() - No indirect function pointers (avoids Phase 85's -0.86% regression) - Fail-fast on LARSON_FIX=1 (cross-thread validation incompatibility) ## Results (10-run SSOT) **NO-GO**: +0.25% improvement (threshold: +1.0%) - Control: 51,750,467 ops/s (CV: 2.26%) - Treatment: 51,881,055 ops/s (CV: 2.32%) - Delta: +0.25% (mean), -0.15% (median) ## Root Cause Competing optimizations plateau: 1. Phase 9/10 MONO LEGACY (+1.89%) already capture most free path benefit 2. Remaining margin insufficient to overcome: - Two branch checks (mask_enabled + has_class) - I-cache layout tax in hot path - Direct function call overhead ## Phase 85 vs Phase 86 | Metric | Phase 85 | Phase 86 | |--------|----------|----------| | Approach | Indirect calls + table | Bitset mask + direct call | | Result | -0.86% | +0.25% | | Verdict | NO-GO (regression) | NO-GO (insufficient) | Phase 86 correctly avoided indirect call penalties but revealed architectural limit: can't escape Phase 9/10 overlay without restructuring. ## Recommendation Free path optimization layer has reached practical ceiling: - Phase 9/10 +1.89% + Phase 6/19/FASTLANE +16-27% ≈ 18-29% total - Further attempts on ceremony elimination face same constraints - Recommend focus on different optimization layers (malloc, etc.) ## Files Changed ### New - core/box/free_path_legacy_mask_box.h (API + globals) - core/box/free_path_legacy_mask_box.c (refresh logic) ### Modified - core/bench_profile.h (added refresh call) - core/front/malloc_tiny_fast.h (added Phase 86 fast path check) - Makefile (added object files) - CURRENT_TASK.md (documented result) All changes conditional on HAKMEM_FREE_PATH_LEGACY_MASK=1 (default OFF). 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
This commit is contained in:
Moe Charm (CI)
@ -17,6 +17,8 @@
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#include "box/fastlane_direct_env_box.h" // fastlane_direct_env_refresh_from_env (Phase 19-1)
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#include "box/tiny_header_hotfull_env_box.h" // tiny_header_hotfull_env_refresh_from_env (Phase 21)
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#include "box/tiny_inline_slots_fixed_mode_box.h" // tiny_inline_slots_fixed_mode_refresh_from_env (Phase 78-1)
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#include "box/free_path_commit_once_fixed_box.h" // free_path_commit_once_refresh_from_env (Phase 85)
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#include "box/free_path_legacy_mask_box.h" // free_path_legacy_mask_refresh_from_env (Phase 86)
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#endif
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// env が未設定のときだけ既定値を入れる
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@ -235,5 +237,9 @@ static inline void bench_apply_profile(void) {
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tiny_header_hotfull_env_refresh_from_env();
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// Phase 78-1: Optionally pin C3/C4/C5/C6 inline-slots modes (avoid per-op ENV gates).
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tiny_inline_slots_fixed_mode_refresh_from_env();
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// Phase 85: Optionally commit-once for C4-C7 LEGACY free path (skip policy/route/mono ceremony).
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free_path_commit_once_refresh_from_env();
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// Phase 86: Optionally use legacy mask for early exit (no indirect calls, just bit test).
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free_path_legacy_mask_refresh_from_env();
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#endif
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}
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105
core/box/free_path_commit_once_fixed_box.c
Normal file
105
core/box/free_path_commit_once_fixed_box.c
Normal file
@ -0,0 +1,105 @@
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// free_path_commit_once_fixed_box.c - Phase 85: Free Path Commit-Once (LEGACY-only)
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#include "free_path_commit_once_fixed_box.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include "tiny_route_env_box.h"
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#include "free_policy_fast_v2_box.h"
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#include "tiny_legacy_fallback_box.h"
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#include "hakmem_build_flags.h"
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#define TINY_C4 4
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#define TINY_C7 7
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// ============================================================================
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// Global state
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// ============================================================================
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uint8_t g_free_path_commit_once_enabled = 0;
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struct FreePatchCommitOnceEntry g_free_path_commit_once_entries[4] = {0};
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// ============================================================================
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// Refresh from ENV (called by bench_profile)
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// ============================================================================
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void free_path_commit_once_refresh_from_env(void) {
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// 1. Read master ENV gate
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const char* env_val = getenv("HAKMEM_FREE_PATH_COMMIT_ONCE");
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int requested = (env_val && *env_val && *env_val != '0') ? 1 : 0;
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if (!requested) {
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g_free_path_commit_once_enabled = 0;
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return;
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}
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// 2. Fail-fast: LARSON_FIX incompatible with commit-once
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// owner_tid validation must happen on every free, cannot commit-once
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const char* larson_env = getenv("HAKMEM_TINY_LARSON_FIX");
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int larson_fix_enabled = (larson_env && *larson_env && *larson_env != '0') ? 1 : 0;
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if (larson_fix_enabled) {
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_PATH_COMMIT_ONCE] FAIL-FAST: HAKMEM_TINY_LARSON_FIX=1 incompatible, disabling\n");
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fflush(stderr);
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#endif
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g_free_path_commit_once_enabled = 0;
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return;
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}
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// 3. Ensure route snapshot is initialized
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tiny_route_snapshot_init();
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// 4. Get nonlegacy mask (classes that use ULTRA/MID/V7)
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uint8_t nonlegacy_mask = free_policy_fast_v2_nonlegacy_mask();
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// 5. For each C4-C7 class, determine if it can commit-once
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// Commit-once is safe if:
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// - Class is NOT in nonlegacy_mask (implies LEGACY route)
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// - Route snapshot confirms TINY_ROUTE_LEGACY
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for (int i = 0; i < 4; i++) {
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unsigned class_idx = TINY_C4 + i;
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struct FreePatchCommitOnceEntry* entry = &g_free_path_commit_once_entries[i];
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// Initialize entry
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entry->can_commit = 0;
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entry->handler = NULL;
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// Check if class is in nonlegacy mask
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if ((nonlegacy_mask & (1u << class_idx)) != 0) {
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// Class uses non-legacy path (ULTRA/MID/V7)
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continue;
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}
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// Check route snapshot
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tiny_route_kind_t route = tiny_route_for_class((uint8_t)class_idx);
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if (route != TINY_ROUTE_LEGACY) {
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// Unexpected route (should not happen if nonlegacy_mask is correct)
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_PATH_COMMIT_ONCE] FAIL-FAST: C%u route=%d not LEGACY, disabling\n",
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class_idx, (int)route);
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fflush(stderr);
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#endif
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g_free_path_commit_once_enabled = 0;
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return;
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}
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// Route is LEGACY and class not in nonlegacy_mask: safe to commit-once
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entry->can_commit = 1;
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entry->handler = tiny_legacy_fallback_free_base_with_env;
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_PATH_COMMIT_ONCE] C%u committed (handler=%p)\n",
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class_idx, (void*)entry->handler);
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fflush(stderr);
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#endif
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}
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// 6. All checks passed, enable commit-once
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g_free_path_commit_once_enabled = 1;
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_PATH_COMMIT_ONCE] Enabled (nonlegacy_mask=0x%02x, LARSON_FIX=0)\n", nonlegacy_mask);
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fflush(stderr);
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#endif
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}
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49
core/box/free_path_commit_once_fixed_box.h
Normal file
49
core/box/free_path_commit_once_fixed_box.h
Normal file
@ -0,0 +1,49 @@
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// free_path_commit_once_fixed_box.h - Phase 85: Free Path Commit-Once (LEGACY-only)
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//
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// Goal: Eliminate per-operation policy/route/mono ceremony overhead for C4-C7 LEGACY classes
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// by pre-computing route+handler at init-time.
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//
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// Design (Box Theory, adapted from Phase 78-1):
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// - Single boundary: bench_profile calls free_path_commit_once_refresh_from_env()
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// after applying presets.
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// - Cache: Pre-compute for each C4-C7 class whether it can use commit-once path
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// (must be LEGACY route AND LARSON_FIX disabled)
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// - Hot path: If commit-once enabled and class in commit set, skip Phase 9/10/policy/route
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// ceremony and call handler directly.
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// - Reversible: toggle HAKMEM_FREE_PATH_COMMIT_ONCE=0/1.
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//
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// Fail-fast: If HAKMEM_TINY_LARSON_FIX=1, disable commit-once (owner_tid validation
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// incompatible with early exit).
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//
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// ENV:
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// - HAKMEM_FREE_PATH_COMMIT_ONCE=0/1 (default 0)
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#ifndef HAK_BOX_FREE_PATH_COMMIT_ONCE_FIXED_BOX_H
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#define HAK_BOX_FREE_PATH_COMMIT_ONCE_FIXED_BOX_H
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#include <stdint.h>
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#include "tiny_route_env_box.h"
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// Forward declaration: handler function pointer
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typedef void (*FreeTinyHandler)(void* base, uint32_t class_idx, const struct HakmemEnvSnapshot* env);
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// Cached entry for a single class (C4-C7)
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struct FreePatchCommitOnceEntry {
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uint8_t can_commit; // 1 if this class can use commit-once, 0 otherwise
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FreeTinyHandler handler; // Handler function pointer (if can_commit=1)
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};
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// Refresh (single boundary): bench_profile calls this after putenv defaults.
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void free_path_commit_once_refresh_from_env(void);
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// Cached state (read in hot path).
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extern uint8_t g_free_path_commit_once_enabled;
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extern struct FreePatchCommitOnceEntry g_free_path_commit_once_entries[4]; // C4-C7
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// Fast-path API (inlined)
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__attribute__((always_inline))
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static inline int free_path_commit_once_enabled_fast(void) {
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return (int)g_free_path_commit_once_enabled;
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}
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#endif // HAK_BOX_FREE_PATH_COMMIT_ONCE_FIXED_BOX_H
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88
core/box/free_path_legacy_mask_box.c
Normal file
88
core/box/free_path_legacy_mask_box.c
Normal file
@ -0,0 +1,88 @@
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// free_path_legacy_mask_box.c - Phase 86: Free Path Legacy Mask (mask-only)
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#include "free_path_legacy_mask_box.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include "tiny_route_env_box.h"
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#include "free_policy_fast_v2_box.h"
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#include "tiny_c7_ultra_box.h"
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#include "hakmem_build_flags.h"
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#define TINY_C0 0
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#define TINY_C7 7
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// ============================================================================
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// Global state
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// ============================================================================
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uint8_t g_free_legacy_mask_enabled = 0;
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uint8_t g_free_legacy_mask = 0;
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// ============================================================================
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// Refresh from ENV (called by bench_profile)
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// ============================================================================
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void free_path_legacy_mask_refresh_from_env(void) {
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// 1. Read master ENV gate
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const char* env_val = getenv("HAKMEM_FREE_PATH_LEGACY_MASK");
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int requested = (env_val && *env_val && *env_val != '0') ? 1 : 0;
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if (!requested) {
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g_free_legacy_mask_enabled = 0;
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return;
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}
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// 2. Fail-fast: LARSON_FIX incompatible
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// owner_tid validation must happen on every free, cannot commit-once
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const char* larson_env = getenv("HAKMEM_TINY_LARSON_FIX");
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int larson_fix_enabled = (larson_env && *larson_env && *larson_env != '0') ? 1 : 0;
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if (larson_fix_enabled) {
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_LEGACY_MASK] FAIL-FAST: HAKMEM_TINY_LARSON_FIX=1 incompatible, disabling\n");
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fflush(stderr);
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#endif
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g_free_legacy_mask_enabled = 0;
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return;
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}
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// 3. Ensure route snapshot is initialized
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tiny_route_snapshot_init();
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// 4. Get nonlegacy mask (classes that use ULTRA/MID/V7)
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uint8_t nonlegacy_mask = free_policy_fast_v2_nonlegacy_mask();
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// 5. Check if C7 ULTRA is enabled (special case: C7 has ULTRA fast path)
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int c7_ultra_enabled = tiny_c7_ultra_enabled_env();
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// 6. Compute legacy_mask: bit i = 1 if class i is LEGACY (not in nonlegacy_mask)
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// and route confirms LEGACY
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uint8_t mask = 0;
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for (unsigned i = TINY_C0; i <= TINY_C7; i++) {
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// Skip if class is in non-legacy mask (ULTRA/MID/V7 active)
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if (nonlegacy_mask & (1u << i)) {
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continue;
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}
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// Skip if C7 and ULTRA is enabled (C7 ULTRA has dedicated fast path)
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if (i == 7 && c7_ultra_enabled) {
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continue;
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}
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// Check route snapshot
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tiny_route_kind_t route = tiny_route_for_class((uint8_t)i);
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if (route == TINY_ROUTE_LEGACY) {
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mask |= (1u << i);
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}
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}
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g_free_legacy_mask = mask;
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g_free_legacy_mask_enabled = 1;
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#if !HAKMEM_BUILD_RELEASE
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fprintf(stderr, "[FREE_LEGACY_MASK] enabled=1 mask=0x%02x nonlegacy=0x%02x c7_ultra=%d larson=0\n",
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mask, nonlegacy_mask, c7_ultra_enabled);
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fflush(stderr);
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#endif
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}
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46
core/box/free_path_legacy_mask_box.h
Normal file
46
core/box/free_path_legacy_mask_box.h
Normal file
@ -0,0 +1,46 @@
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// free_path_legacy_mask_box.h - Phase 86: Free Path Legacy Mask (mask-only, no indirect calls)
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//
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// Goal: Achieve Phase 10 effect (skip ceremony for LEGACY classes) with lower cost by:
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// - Computing legacy_mask at init-time (bench_profile boundary)
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// - Avoiding indirect call overhead (no function pointers)
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// - Single direct call to tiny_legacy_fallback_free_base_with_env()
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// - No table lookups in hot path (just bit test)
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//
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// Design (Box Theory):
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// - Single boundary: bench_profile calls free_path_legacy_mask_refresh_from_env()
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// after applying presets (putenv defaults).
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// - Cache: legacy_mask (bitset, 1 bit per class C0-C7)
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// - Hot path: If enabled and (mask & (1 << class_idx)), skip policy/route/mono ceremony
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// and call tiny_legacy_fallback_free_base_with_env() directly.
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// - Reversible: toggle HAKMEM_FREE_PATH_LEGACY_MASK=0/1.
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//
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// Fail-fast: If HAKMEM_TINY_LARSON_FIX=1, disable (cross-thread owner_tid validation needed).
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//
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// ENV:
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// - HAKMEM_FREE_PATH_LEGACY_MASK=0/1 (default 0)
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#ifndef HAK_BOX_FREE_PATH_LEGACY_MASK_BOX_H
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#define HAK_BOX_FREE_PATH_LEGACY_MASK_BOX_H
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#include <stdint.h>
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// Refresh (single boundary): bench_profile calls this after putenv defaults.
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void free_path_legacy_mask_refresh_from_env(void);
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// Cached state (read in hot path).
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extern uint8_t g_free_legacy_mask_enabled;
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extern uint8_t g_free_legacy_mask; // Bitset: bit i = 1 if class i is LEGACY and can skip ceremony
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// Fast-path API (inlined, no fallback needed).
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__attribute__((always_inline))
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static inline int free_path_legacy_mask_enabled_fast(void) {
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return (int)g_free_legacy_mask_enabled;
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}
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__attribute__((always_inline))
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static inline int free_path_legacy_mask_has_class(unsigned class_idx) {
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if (__builtin_expect(class_idx >= 8, 0)) return 0;
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return (g_free_legacy_mask & (1u << class_idx)) ? 1 : 0;
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}
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#endif // HAK_BOX_FREE_PATH_LEGACY_MASK_BOX_H
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@ -74,6 +74,8 @@
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#include "../box/free_cold_shape_stats_box.h" // Phase 5 E5-3a: Free cold shape stats
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#include "../box/free_tiny_fast_mono_dualhot_env_box.h" // Phase 9: MONO DUALHOT ENV gate
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#include "../box/free_tiny_fast_mono_legacy_direct_env_box.h" // Phase 10: MONO LEGACY DIRECT ENV gate
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#include "../box/free_path_commit_once_fixed_box.h" // Phase 85: Free path commit-once (LEGACY-only)
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#include "../box/free_path_legacy_mask_box.h" // Phase 86: Free path legacy mask (mask-only, no indirect calls)
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#include "../box/alloc_passdown_ssot_env_box.h" // Phase 60: Alloc pass-down SSOT
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// Helper: current thread id (low 32 bits) for owner check
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@ -955,6 +957,39 @@ static inline int free_tiny_fast(void* ptr) {
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// Phase 19-3b: Consolidate ENV snapshot reads (capture once per free_tiny_fast call).
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const HakmemEnvSnapshot* env = hakmem_env_snapshot_enabled() ? hakmem_env_snapshot() : NULL;
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// Phase 86: Free path legacy mask - Direct early exit for LEGACY classes (no indirect calls)
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// Conditions:
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// - ENV: HAKMEM_FREE_PATH_LEGACY_MASK=1
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// - class_idx in legacy_mask (LEGACY route, not ULTRA/MID/V7)
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// - LARSON_FIX=0 (checked at startup, fail-fast if enabled)
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if (__builtin_expect(free_path_legacy_mask_enabled_fast(), 0)) {
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if (__builtin_expect(free_path_legacy_mask_has_class((unsigned)class_idx), 0)) {
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// Direct path: Call legacy handler without policy snapshot, route, or mono checks
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tiny_legacy_fallback_free_base_with_env(base, (uint32_t)class_idx, env);
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return 1;
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}
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}
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||||
// Phase 85: Free path commit-once (LEGACY-only) - Skip policy/route/mono ceremony for committed C4-C7
|
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// Conditions:
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// - ENV: HAKMEM_FREE_PATH_COMMIT_ONCE=1
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// - class_idx in C4-C7 (129-256B LEGACY classes)
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// - Pre-computed at startup that class can use commit-once
|
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// - LARSON_FIX=0 (checked at startup, fail-fast if enabled)
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if (__builtin_expect(free_path_commit_once_enabled_fast(), 0)) {
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if (__builtin_expect((unsigned)class_idx >= 4u && (unsigned)class_idx <= 7u, 0)) {
|
||||
const unsigned cache_idx = (unsigned)class_idx - 4u;
|
||||
const struct FreePatchCommitOnceEntry* entry = &g_free_path_commit_once_entries[cache_idx];
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if (__builtin_expect(entry->can_commit, 0)) {
|
||||
// Direct path: Call handler without policy snapshot, route, or mono checks
|
||||
FREE_PATH_STAT_INC(commit_once_hit);
|
||||
entry->handler(base, (uint32_t)class_idx, env);
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Phase 9: MONO DUALHOT early-exit for C0-C3 (skip policy snapshot, direct to legacy)
|
||||
// Conditions:
|
||||
// - ENV: HAKMEM_FREE_TINY_FAST_MONO_DUALHOT=1
|
||||
|
||||
Reference in New Issue
Block a user