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Update CURRENT_TASK.md: Phase 9-2 Complete (50M ops/s), Phase 10 Planned (Type Safety)

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# Current Task: Phase 9-2 Refactoring (Complete)
# Current Task: Phase 9-2 Refactoring (Complete) & Phase 10 Preparation
**Date**: 2025-11-30
**Status**: **COMPLETE** (Phase 9-2 & Refactoring)
**Goal**: SuperSlab Unified Management, Stability Fixes, and Code Refactoring
**Date**: 2025-12-01
**Status**: **COMPLETE** (Phase 9-2) / **PLANNING** (Phase 10)
**Goal**: Legacy Backend Removal, Shared Pool Unification, and Type Safety
---
## Phase 9-2 Achievements (Completed)
1. **Critical Fixes (Deadlock & OOM)**
* **Deadlock**: `shared_pool_acquire_slab` now releases `alloc_lock` before calling `superslab_allocate` (via `sp_internal_allocate_superslab`), preventing lock inversion with `g_super_reg_lock`.
* **OOM**: Enabled `HAKMEM_TINY_USE_SUPERSLAB=1` by default in `hakmem_build_flags.h`, ensuring fallback to Legacy Backend when Shared Pool hits soft cap.
1. **Legacy Backend Removal & Unification (2025-12-01)**
* **Eliminated Fallback**: Removed `hak_tiny_alloc_superslab_backend_legacy` fallback. Shared Pool is now the sole backend (`hak_tiny_alloc_superslab_box` -> `hak_tiny_alloc_superslab_backend_shared`).
* **Soft Cap Removed**: Removed the artificial "Soft Cap" limit in Shared Pool Stage 3, allowing it to handle full workload load.
* **EMPTY Recycling**: Implemented `SLAB_TRY_RECYCLE` with atomic batch decrement of `meta->used` in `_ss_remote_drain_to_freelist_unsafe`. This ensures EMPTY slabs are immediately returned to the global pool.
* **Race Condition Fix**: Moved `remove_superslab_from_legacy_head(ss)` to the *start* of `shared_pool_release_slab` to prevent Legacy Backend from allocating from a slab being recycled. Added `total_active_blocks` check before freeing.
* **Performance**: **50.3 M ops/s** in WS8192 benchmark (vs 16.5 M baseline). OOM/Crash issues resolved.
2. **SuperSlab Management Unification**
* **Unified Entry**: `sp_internal_allocate_superslab` helper introduced to manage safe allocation flow.
* **Unified Free**: `remove_superslab_from_legacy_head` implemented to safely remove pointers from legacy lists when freeing via Shared Pool.
2. **Critical Fixes (Deadlock & OOM)**
* **Deadlock**: `shared_pool_acquire_slab` releases `alloc_lock` before `superslab_allocate`.
* **Is Empty Return**: `tiny_free_local_box` now returns `int is_empty` status to allow safe, race-free recycling by the caller.
3. **Code Refactoring (Split `hakmem_shared_pool.c`)**
* **Split Strategy**: Divided the monolithic `core/hakmem_shared_pool.c` (1400+ lines) into logical modules:
* `core/hakmem_shared_pool.c`: Initialization, stats, and common helpers.
* `core/hakmem_shared_pool_acquire.c`: Allocation logic (`shared_pool_acquire_slab` and Stage 0.5-3).
* `core/hakmem_shared_pool_release.c`: Deallocation logic (`shared_pool_release_slab`).
* `core/hakmem_shared_pool_internal.h`: Internal shared definitions and prototypes.
* **Makefile**: Updated to compile and link the new files.
* **Cleanups**: Removed unused "L0 Cache" experimental code and fixed incorrect function names (`superslab_alloc` -> `superslab_allocate`).
3. **Code Refactoring**
* Modularized `hakmem_shared_pool.c` into `acquire/release/internal` components.
---
## Next Phase Candidates (Handover from Phase 9-2)
## Next Phase: Phase 10 - Type Safety & Hardening
### 1. Soft Cap (Policy) Tuning
* **Issue**: Medium Working Sets (8192) hit the Shared Pool "Soft Cap" easily, causing frequent fallbacks and performance degradation.
* **Action**: Review `hakmem_policy.c` and adjust `tiny_cap` or improve dynamic adjustment logic.
### 1. Pointer Type Safety (Debug Only)
* **Issue**: Occasional `[TLS_SLL_HDR_RESET]` warnings indicate confusion between `BasePtr` (header start) and `UserPtr` (payload start).
* **Solution**: Implement "Phantom Type" checking macros enabled only in debug builds.
* Define `hak_base_ptr_t` and `hak_user_ptr_t` structs in debug.
* Define strict conversion macros (`hak_base_to_user`, `hak_user_to_base`).
* Apply incrementally to `tls_sll_box`, `free_local_box`, and `remote_free_box`.
* **Goal**: Catch pointer arithmetic errors at compile time in debug mode.
### 2. Fast Path Optimization
* **Issue**: Small Working Sets (256) show 70-88% performance vs SysAlloc due to lock/call overhead. Refactoring caused a slight dip (15%), highlighting the need for optimization.
* **Action**: Re-implement a lightweight L0 Cache or optimize the lock-free path in Shared Pool for hot-path performance. Consider inlining hot helpers again via header-only implementations if needed.
### 2. Header Protection Hardening
* **Goal**: Reinforce header integrity checks in `tiny_free_local_box` and `tls_sll_pop` using the new type system.
### 3. Legacy Backend Removal
* **Issue**: Legacy Backend (`g_superslab_heads`) is still kept for fallback but causes complexity.
* **Action**: Plan complete removal of `g_superslab_heads`, migrating all management to Shared Pool.
### 3. Fast Path Optimization
* **Goal**: Re-evaluate hot path performance (Stage 1 lock-free) after Phase 9-2 stabilization.
---
## Current Status
* **Build**: Passing (Clean build verified).
* **Benchmarks**:
* `HAKMEM_TINY_SS_SHARED=1` (Normal): ~20.0 M ops/s (working, fallback active).
* `HAKMEM_TINY_SS_SHARED=2` (Strict): ~20.3 M ops/s (working, OOMs on soft cap as expected).
* **Pending**: Selection of next focus area.
* WS8192: **50.3 M ops/s** (Shared Pool ONLY).
* Crash/OOM: Resolved.
* **Pending**: Phase 10 implementation (Type Safety).