hakmem/core/hakmem_tiny_config.h

/**
 * hakmem_tiny_config.h
 *
 * Centralized Configuration for TinyPool (≤1KB allocations)
 * All tunable constants and defaults in one place
 *
 * Created: 2025-11-01
 * Purpose: Simplify tuning and avoid scattered magic numbers
 */

#ifndef HAKMEM_TINY_CONFIG_H
#define HAKMEM_TINY_CONFIG_H

#include <stdint.h>
#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

// ============================================================================
// Size Classes (8 classes: 8B, 16B, 32B, 64B, 128B, 256B, 512B, 1KB)
// ============================================================================

#define TINY_NUM_CLASSES 8

// Size class boundaries (defined in hakmem_tiny.h, referenced here)
extern const size_t g_tiny_class_sizes[TINY_NUM_CLASSES];

// ============================================================================
// Fast Cache Configuration (per-class front-end cache)
// ============================================================================

// Default fast cache capacities per class (mutable so presets/env can tweak)
extern uint16_t g_fast_cap_defaults[TINY_NUM_CLASSES];

// Reset fast cache defaults back to the factory baseline
void tiny_config_reset_defaults(void);

// ============================================================================
// TLS Magazine Configuration (thread-local cache)
// ============================================================================

// Global magazine capacity limit (can be overridden by HAKMEM_TINY_MAG_CAP)
#define TINY_TLS_MAG_CAP 2048

// Default TLS magazine capacities per class
// These are the initial/default values before ACE learning adjusts them
// Implemented in hakmem_tiny_config.c
int tiny_default_cap(int class_idx);
int tiny_mag_default_cap(int class_idx);  // Alias for tiny_default_cap

// Maximum allowed TLS magazine capacities per class
// These limits prevent ACE from growing caches too large
// Implemented in hakmem_tiny_config.c
int tiny_cap_max_for_class(int class_idx);

// ============================================================================
// SuperSlab Configuration (1MB aligned chunks)
// ============================================================================

// SuperSlab constants are defined in hakmem_tiny_superslab.h to avoid duplication
// - SUPERSLAB_SIZE: 1MB (default)
// - SLABS_PER_SUPERSLAB: 256 (for 1MB SuperSlab)
// - SUPERSLAB_MAGIC: Magic number for validation

// ============================================================================
// Partial SuperSlab Release Configuration
// ============================================================================

// Enable partial SuperSlab release by default
// When enabled, SuperSlabs with low active block count are released via madvise
#define TINY_SS_PARTIAL_ENABLE_DEFAULT 1

// Partial release interval (every N refills)
#define TINY_SS_PARTIAL_INTERVAL_DEFAULT 4

// Active block threshold for partial release (percentage)
// If active_blocks / capacity < threshold, release the SuperSlab
#define TINY_SS_PARTIAL_THRESHOLD_PCT_DEFAULT 10  // 10%

// ============================================================================
// Refill/Drain Configuration
// ============================================================================

// Number of blocks to refill from SuperSlab to magazine
#define TINY_REFILL_BATCH_SIZE 16

// Number of blocks to drain from magazine to SuperSlab
#define TINY_DRAIN_BATCH_SIZE 16

// ============================================================================
// Remote Free Configuration (cross-thread free)
// ============================================================================

// Remote free list capacity per class
#define TINY_REMOTE_FREE_CAP 64

// Batch size for draining remote free list
#define TINY_REMOTE_DRAIN_BATCH 32

// ============================================================================
// Memory Efficiency Presets
// ============================================================================

// Preset: Balanced (default)
// - Moderate cache sizes
// - Partial release enabled
// - Good balance between performance and RSS
#define TINY_PRESET_BALANCED() tiny_config_reset_defaults()

// Preset: Tight (low memory)
// - Smaller cache sizes
// - Aggressive partial release
// - Optimized for RSS at slight performance cost
#define TINY_PRESET_TIGHT() do { \
    g_fast_cap_defaults[0] = 64;  /* 8B */ \
    g_fast_cap_defaults[1] = 64;  /* 16B */ \
    g_fast_cap_defaults[2] = 64;  /* 32B */ \
    g_fast_cap_defaults[3] = 64;  /* 64B */ \
    g_fast_cap_defaults[4] = 64;  /* 128B */ \
    g_fast_cap_defaults[5] = 64;  /* 256B */ \
    g_fast_cap_defaults[6] = 64;  /* 512B */ \
} while(0)

// Preset: Ultra Tight (minimal memory)
// - Minimal cache sizes
// - Maximum RSS reduction
// - Use for memory-constrained environments
#define TINY_PRESET_ULTRA_TIGHT() do { \
    g_fast_cap_defaults[0] = 32;  /* 8B */ \
    g_fast_cap_defaults[1] = 32;  /* 16B */ \
    g_fast_cap_defaults[2] = 32;  /* 32B */ \
    g_fast_cap_defaults[3] = 32;  /* 64B */ \
    g_fast_cap_defaults[4] = 32;  /* 128B */ \
    g_fast_cap_defaults[5] = 32;  /* 256B */ \
    g_fast_cap_defaults[6] = 32;  /* 512B */ \
} while(0)

// ============================================================================
// Environment Variable Overrides
// ============================================================================

// The following environment variables can override defaults:
//
// - HAKMEM_TINY_MAG_CAP:         Global magazine cap limit
// - HAKMEM_TINY_MAG_CAP_C{0..7}: Per-class magazine cap override
// - HAKMEM_TINY_SS_PARTIAL:      Enable/disable partial release (0/1)
// - HAKMEM_TINY_SS_PARTIAL_INT:  Partial release interval
// - HAKMEM_TINY_SS_PARTIAL_PCT:  Partial release threshold percentage
//
// Example:
//   HAKMEM_TINY_MAG_CAP=512 HAKMEM_TINY_SS_PARTIAL=1 ./my_app

#ifdef __cplusplus
}
#endif

#endif // HAKMEM_TINY_CONFIG_H