7adbcdfcb6
## Summary
Completed Phase 54-60 optimization work:
**Phase 54-56: Memory-Lean mode (LEAN+OFF prewarm suppression)**
- Implemented ss_mem_lean_env_box.h with ENV gates
- Balanced mode (LEAN+OFF) promoted as production default
- Result: +1.2% throughput, better stability, zero syscall overhead
- Added to bench_profile.h: MIXED_TINYV3_C7_BALANCED preset
**Phase 57: 60-min soak finalization**
- Balanced mode: 60-min soak, RSS drift 0%, CV 5.38%
- Speed-first mode: 60-min soak, RSS drift 0%, CV 1.58%
- Syscall budget: 1.25e-7/op (800× under target)
- Status: PRODUCTION-READY
**Phase 59: 50% recovery baseline rebase**
- hakmem FAST (Balanced): 59.184M ops/s, CV 1.31%
- mimalloc: 120.466M ops/s, CV 3.50%
- Ratio: 49.13% (M1 ACHIEVED within statistical noise)
- Superior stability: 2.68× better CV than mimalloc
**Phase 60: Alloc pass-down SSOT (NO-GO)**
- Implemented alloc_passdown_ssot_env_box.h
- Modified malloc_tiny_fast.h for SSOT pattern
- Result: -0.46% (NO-GO)
- Key lesson: SSOT not applicable where early-exit already optimized
## Key Metrics
- Performance: 49.13% of mimalloc (M1 effectively achieved)
- Stability: CV 1.31% (superior to mimalloc 3.50%)
- Syscall budget: 1.25e-7/op (excellent)
- RSS: 33MB stable, 0% drift over 60 minutes
## Files Added/Modified
New boxes:
- core/box/ss_mem_lean_env_box.h
- core/box/ss_release_policy_box.{h,c}
- core/box/alloc_passdown_ssot_env_box.h
Scripts:
- scripts/soak_mixed_single_process.sh
- scripts/analyze_epoch_tail_csv.py
- scripts/soak_mixed_rss.sh
- scripts/calculate_percentiles.py
- scripts/analyze_soak.py
Documentation: Phase 40-60 analysis documents
## Design Decisions
1. Profile separation (core/bench_profile.h):
- MIXED_TINYV3_C7_SAFE: Speed-first (no LEAN)
- MIXED_TINYV3_C7_BALANCED: Balanced mode (LEAN+OFF)
2. Box Theory compliance:
- All ENV gates reversible (HAKMEM_SS_MEM_LEAN, HAKMEM_ALLOC_PASSDOWN_SSOT)
- Single conversion points maintained
- No physical deletions (compile-out only)
3. Lessons learned:
- SSOT effective only where redundancy exists (Phase 60 showed limits)
- Branch prediction extremely effective (~0 cycles for well-predicted branches)
- Early-exit pattern valuable even when seemingly redundant
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
73 lines
2.5 KiB
C
73 lines
2.5 KiB
C
// ss_release_policy_box.h - SuperSlab Release Policy Box
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// Purpose: Determine when to keep/release/decommit superslabs (Memory-Lean mode)
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// Box Theory: Single conversion point for superslab lifecycle decisions
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//
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// Responsibilities:
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// - Decide if a superslab should be kept (persistent) or released
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// - Execute decommit operations (MADV_FREE/MADV_DONTNEED) when lean mode enabled
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// - Respect DSO guard / fail-fast rules (never touch DSO memory)
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//
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// Design Philosophy:
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// - In FAST mode (default): Keep all superslabs (speed-first, persistent backend)
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// - In LEAN mode (opt-in): Release empty superslabs to reduce RSS
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// - Boundary: All decommit operations flow through Superslab OS Box (ss_os_madvise_guarded)
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// - Safety: DSO guard prevents touching .fini_array (Phase 17 lesson)
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//
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// Dependencies:
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// - ss_mem_lean_env_box.h (ENV configuration)
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// - madvise_guard_box.h (DSO-safe madvise wrapper)
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// - ss_os_acquire_box.h (stats counters)
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//
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// License: MIT
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// Date: 2025-12-17
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#ifndef HAKMEM_SS_RELEASE_POLICY_BOX_H
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#define HAKMEM_SS_RELEASE_POLICY_BOX_H
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#include <stdint.h>
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#include <stddef.h>
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#include <stdbool.h>
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// Forward declaration
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struct SuperSlab;
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typedef struct SuperSlab SuperSlab;
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// ============================================================================
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// Release Policy API
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// ============================================================================
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// Check if a superslab should be kept in memory (persistent backend)
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//
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// Returns:
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// - true: Keep superslab (FAST mode, or LEAN mode with budget remaining)
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// - false: Release superslab (LEAN mode, empty and over budget)
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//
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// Parameters:
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// - ss: SuperSlab to check
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// - class_idx: Size class (0-7 for Tiny)
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//
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// Thread-safe: Yes (reads ENV config, no shared state)
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bool ss_should_keep_superslab(SuperSlab* ss, int class_idx);
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// Attempt to decommit a superslab's memory (reduce RSS)
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//
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// What it does:
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// - If lean mode disabled: no-op (return immediately)
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// - If lean mode enabled: call madvise(MADV_FREE or MADV_DONTNEED)
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// - Respects DSO guard (skips if address overlaps DSO)
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// - Respects madvise guard (disables on ENOMEM)
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// - Updates lean_decommit counter on success
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//
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// Returns:
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// - 0: Success (or no-op if lean mode disabled)
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// - -1: Failed (DSO overlap, madvise error, etc.)
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//
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// Parameters:
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// - ptr: Start of memory region
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// - size: Size of memory region in bytes
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//
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// Thread-safe: Yes (no shared state mutations except atomic counters)
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int ss_maybe_decommit_superslab(void* ptr, size_t size);
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#endif // HAKMEM_SS_RELEASE_POLICY_BOX_H
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