74 lines
2.7 KiB
C
74 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 Phase 6-2.5)
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// Actual value: sizeof(SuperSlab) = 1088 bytes
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// This includes: magic, lg_size, size_class, total_active_blocks,
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// remote_heads[], slabs[], slab_listed[], etc.
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#define SUPERSLAB_HEADER_SIZE 1088
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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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