dc9e650db3
This commit implements the first phase of Tiny Pool redesign based on
ChatGPT architecture review. The goal is to eliminate Header/Next pointer
conflicts by moving class_idx lookup out-of-band (to SuperSlab metadata).
## P0.1: C0(8B) class upgraded to 16B
- Size table changed: {16,32,64,128,256,512,1024,2048} (8 classes)
- LUT updated: 1..16 → class 0, 17..32 → class 1, etc.
- tiny_next_off: C0 now uses offset 1 (header preserved)
- Eliminates edge cases for 8B allocations
## P0.3: Slab reuse guard Box (tls_slab_reuse_guard_box.h)
- New Box for draining TLS SLL before slab reuse
- ENV gate: HAKMEM_TINY_SLAB_REUSE_GUARD=1
- Prevents stale pointers when slabs are recycled
- Follows Box theory: single responsibility, minimal API
## P1.1: SuperSlab class_map addition
- Added uint8_t class_map[SLABS_PER_SUPERSLAB_MAX] to SuperSlab
- Maps slab_idx → class_idx for out-of-band lookup
- Initialized to 255 (UNASSIGNED) on SuperSlab creation
- Set correctly on slab initialization in all backends
## P1.2: Free fast path uses class_map
- ENV gate: HAKMEM_TINY_USE_CLASS_MAP=1
- Free path can now get class_idx from class_map instead of Header
- Falls back to Header read if class_map returns invalid value
- Fixed Legacy Backend dynamic slab initialization bug
## Documentation added
- HAKMEM_ARCHITECTURE_OVERVIEW.md: 4-layer architecture analysis
- TLS_SLL_ARCHITECTURE_INVESTIGATION.md: Root cause analysis
- PTR_LIFECYCLE_TRACE_AND_ROOT_CAUSE_ANALYSIS.md: Pointer tracking
- TINY_REDESIGN_CHECKLIST.md: Implementation roadmap (P0-P3)
## Test results
- Baseline: 70% success rate (30% crash - pre-existing issue)
- class_map enabled: 70% success rate (same as baseline)
- Performance: ~30.5M ops/s (unchanged)
## Next steps (P1.3, P2, P3)
- P1.3: Add meta->active for accurate TLS/freelist sync
- P2: TLS SLL redesign with Box-based counting
- P3: Complete Header out-of-band migration
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
75 lines
2.7 KiB
C
75 lines
2.7 KiB
C
// hakmem_tiny_superslab_constants.h - SuperSlab Layout Constants
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// Purpose: Centralize all SuperSlab layout magic numbers
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// Phase 6-2.5: Created to fix sizeof(SuperSlab) vs hardcoded offset mismatch
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#ifndef HAKMEM_TINY_SUPERSLAB_CONSTANTS_H
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#define HAKMEM_TINY_SUPERSLAB_CONSTANTS_H
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// ============================================================================
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// SuperSlab Layout Constants
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// ============================================================================
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// Log2 range for SuperSlab sizes (in MB):
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// - MIN: 1MB (2^20)
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// - MAX: 2MB (2^21)
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// - DEFAULT: 2MB unless constrained by ACE/env
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#ifndef SUPERSLAB_LG_MIN
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#define SUPERSLAB_LG_MIN 20
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#endif
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#ifndef SUPERSLAB_LG_MAX
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#define SUPERSLAB_LG_MAX 21
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#endif
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#ifndef SUPERSLAB_LG_DEFAULT
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#define SUPERSLAB_LG_DEFAULT 21
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#endif
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// Size of each slab within SuperSlab (fixed, never changes)
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#define SLAB_SIZE (64 * 1024) // 64KB per slab
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// SuperSlab struct size (as of P1.1)
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// Actual value: sizeof(SuperSlab) = 1192 bytes
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// This includes: magic, lg_size, size_class, total_active_blocks,
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// remote_heads[], slabs[], slab_listed[], class_map[], etc.
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// P1.1: Added class_map[32] (+32 bytes) for out-of-band class_idx lookup
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#define SUPERSLAB_HEADER_SIZE 1192
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// Slab 0 data offset (CRITICAL: Must be aligned to largest block size)
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// Phase 6-2.5 FIX: Changed from 1024 to 2048
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//
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// Why 2048?
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// - sizeof(SuperSlab) = 1088 bytes
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// - Largest block size = 1024 bytes (class 7)
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// - Must round up to next 1024-byte boundary: (1088 + 1023) & ~1023 = 2048
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//
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// Layout:
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// [0..1087] SuperSlab header (1088 bytes)
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// [1088..2047] Padding (960 bytes, unused)
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// [2048..65535] Slab 0 data (63488 bytes = 64KB - 2048)
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//
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// Previous value (1024) caused:
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// - 64-byte overlap with SuperSlab metadata (corruption)
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// - Misalignment for class 7 allocations (1024 % 1024 != 0)
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#define SUPERSLAB_SLAB0_DATA_OFFSET 2048
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// Slab 0 usable size (for capacity calculation)
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#define SUPERSLAB_SLAB0_USABLE_SIZE (SLAB_SIZE - SUPERSLAB_SLAB0_DATA_OFFSET) // 63488 bytes
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// Regular slab (i > 0) usable size
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#define SUPERSLAB_SLAB_USABLE_SIZE SLAB_SIZE // 65536 bytes
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// ============================================================================
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// Validation (compile-time check)
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// ============================================================================
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// Ensure SLAB0_DATA_OFFSET is aligned to largest block size (1024)
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#if (SUPERSLAB_SLAB0_DATA_OFFSET % 1024) != 0
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#error "SUPERSLAB_SLAB0_DATA_OFFSET must be 1024-byte aligned for class 7"
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#endif
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// Ensure SLAB0_DATA_OFFSET is large enough to contain SuperSlab header
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#if SUPERSLAB_SLAB0_DATA_OFFSET < SUPERSLAB_HEADER_SIZE
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#error "SUPERSLAB_SLAB0_DATA_OFFSET must be >= sizeof(SuperSlab)"
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#endif
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#endif // HAKMEM_TINY_SUPERSLAB_CONSTANTS_H
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