hakmem/core/tiny_refill.h

// tiny_refill.h - Refill Boundary box (inline helpers)
#pragma once
#include <stdatomic.h>
#include "hakmem_tiny_superslab.h"
#include "hakmem_trace_master.h"  // Phase 4c: Master trace control
#include "slab_handle.h"
#include "tiny_sticky.h"
#include "tiny_ready.h"
#include "box/mailbox_box.h"
#include "tiny_remote_bg.h"  // Background remote-drain step (best-effort)
#include "tiny_ready_bg.h"   // Ready aggregator (mailbox→ready hint)
#include "tiny_route.h"       // Route Fingerprint (Box boundary tracing)
#include <stdio.h>
#include <stdlib.h>

// External helpers from main TU
static inline uint32_t tiny_self_u32(void);
static inline void tiny_tls_bind_slab(TinyTLSSlab* tls, SuperSlab* ss, int slab_idx);

// Forward decls in main TU
static inline uintptr_t hot_slot_pop(int class_idx);
static inline uintptr_t bench_pub_pop(int class_idx);
static inline SuperSlab* slab_entry_ss(uintptr_t ent);
static inline int slab_entry_idx(uintptr_t ent);

// Mailbox/Ready consumption always allowed (ENV gate removed)
static inline int tiny_mail_ready_allowed(void) { return 1; }

// Registry scan window (ENV: HAKMEM_TINY_REG_SCAN_MAX, default 256)
static inline int tiny_reg_scan_max(void) {
    static int v = -1;
    if (__builtin_expect(v == -1, 0)) {
        const char* s = getenv("HAKMEM_TINY_REG_SCAN_MAX");
        int defv = 256;  // conservative default
        if (s && *s) {
            int parsed = atoi(s);
            v = (parsed > 0) ? parsed : defv;
        } else {
            v = defv;
        }
    }
    return v;
}

// Opportunistic background remote-drain knobs (ENV removed; fixed defaults)
static inline int tiny_bg_remote_tryrate(void) { return 16; }
static inline int tiny_bg_remote_budget_default(void) { return 2; }

// Mid-size simple refill (ENV: HAKMEM_TINY_MID_REFILL_SIMPLE)
static inline int tiny_mid_refill_simple_enabled(void) {
    static int v = -1;
    if (__builtin_expect(v == -1, 0)) {
        const char* s = getenv("HAKMEM_TINY_MID_REFILL_SIMPLE");
        v = (s && *s && *s != '0') ? 1 : 0;
    }
    return v;
}

// Try a quick adopt from sticky/hot/bench/mailbox (single pass)
static inline SuperSlab* tiny_refill_try_fast(int class_idx, TinyTLSSlab* tls) {
    ROUTE_BEGIN(class_idx); ROUTE_MARK(0);
    // Ready list (Box: Ready) — O(1) candidates published by free/publish
    {
        const int rb = 1; // Ready budget fixed (ENV removed)
        for (int attempt = 0; attempt < rb; attempt++) {
            ROUTE_MARK(1); // ready_try
            uintptr_t ent = tiny_mail_ready_allowed() ? tiny_ready_pop(class_idx) : (uintptr_t)0;
            if (!ent) break;
            SuperSlab* rss = slab_entry_ss(ent);
            int ridx = slab_entry_idx(ent);
            uint32_t self_tid = tiny_self_u32();
            SlabHandle h = slab_try_acquire(rss, ridx, self_tid);
            if (slab_is_valid(&h)) {
                if (slab_remote_pending(&h)) {
                    slab_drain_remote_full(&h);
                    slab_release(&h);
                } else if (slab_is_safe_to_bind(&h)) {
                    tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                    tiny_sticky_save(class_idx, h.ss, h.slab_idx);
                    extern unsigned long long g_rf_hit_ready[];
                    g_rf_hit_ready[class_idx]++;
                    ROUTE_MARK(2); ROUTE_COMMIT(class_idx, 0x01);
                    return h.ss;
                } else {
                    slab_release(&h);
                }
            }
        }
    }
    // One-shot entry trace (env: HAKMEM_TINY_RF_TRACE or HAKMEM_TRACE=refill)
    // Phase 4c: Now uses hak_trace_check() for unified trace control
#if !HAKMEM_BUILD_RELEASE
    do {
        static int en = -1; static _Atomic int printed[8];
        if (__builtin_expect(en == -1, 0)) {
            en = hak_trace_check("HAKMEM_TINY_RF_TRACE", "refill");
        }
        if (en) {
            int expected = 0;
            (void)atomic_compare_exchange_strong(&printed[class_idx], &expected, 1);
            if (expected == 0) {
                fprintf(stderr, "[RFTRACE] fast-refill enter class=%d\n", class_idx);
            }
        }
    } while (0);
#endif
    // For hot tiny classes (0..3), try mailbox first to avoid deeper scans
    if (class_idx <= 3) {
        uint32_t self_tid = tiny_self_u32();
        ROUTE_MARK(3); // mail_try
        uintptr_t mail = tiny_mail_ready_allowed() ? mailbox_box_fetch(class_idx) : (uintptr_t)0;
        if (mail) {
            SuperSlab* mss = slab_entry_ss(mail);
            int midx = slab_entry_idx(mail);
            SlabHandle h = slab_try_acquire(mss, midx, self_tid);
            if (slab_is_valid(&h)) {
                if (slab_remote_pending(&h)) {
                    slab_drain_remote_full(&h);
                    slab_release(&h);
                } else if (slab_is_safe_to_bind(&h)) {
                    tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                    tiny_sticky_save(class_idx, h.ss, h.slab_idx);
                    ROUTE_MARK(4); ROUTE_COMMIT(class_idx, 0x02);
                    return h.ss;
                } else {
                    slab_release(&h);
                }
            }
        }
    }

    // Sticky ring (Box: SlabHandle)
    uint32_t self_tid = tiny_self_u32();
    for (int r = 0; r < TINY_STICKY_RING; r++) {
        ROUTE_MARK(5); // sticky_try
        SuperSlab* last_ss = g_tls_sticky_ss[class_idx][r];
        if (!(last_ss && last_ss->magic == SUPERSLAB_MAGIC)) { tiny_sticky_clear(class_idx, r); continue; }
        int li = g_tls_sticky_idx[class_idx][r];
        int cap = ss_slabs_capacity(last_ss);
        if (li < 0 || li >= cap) { tiny_sticky_clear(class_idx, r); continue; }

        // Box: Try to acquire ownership
        SlabHandle h = slab_try_acquire(last_ss, li, self_tid);
        if (slab_is_valid(&h)) {
            if (slab_remote_pending(&h)) {
                slab_drain_remote_full(&h);
                if (__builtin_expect(g_debug_remote_guard, 0)) {
                    uintptr_t head = atomic_load_explicit(&h.ss->remote_heads[h.slab_idx], memory_order_relaxed);
                    tiny_remote_watch_note("sticky_remote_pending",
                                           h.ss,
                                           h.slab_idx,
                                           (void*)head,
                                           0xA250u,
                                           self_tid,
                                           0);
                }
                slab_release(&h);
            } else if (slab_is_safe_to_bind(&h)) {
                tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                ROUTE_MARK(6); ROUTE_COMMIT(class_idx, 0x03); return h.ss;
            } else {
                slab_release(&h);
            }
        }

        int has_remote = (atomic_load_explicit(&last_ss->remote_heads[li], memory_order_acquire) != 0);
        if (!has_remote) tiny_sticky_clear(class_idx, r);
    }
    // Hot slot
    {
        ROUTE_MARK(7); // hot_try
        uintptr_t hs = hot_slot_pop(class_idx);
        if (hs) {
            SuperSlab* hss = slab_entry_ss(hs);
            int hidx = slab_entry_idx(hs);

            // Box: Try to acquire ownership
            SlabHandle h = slab_try_acquire(hss, hidx, self_tid);
        if (slab_is_valid(&h)) {
            if (slab_remote_pending(&h)) {
                slab_drain_remote_full(&h);
                if (__builtin_expect(g_debug_remote_guard, 0)) {
                    uintptr_t head = atomic_load_explicit(&h.ss->remote_heads[h.slab_idx], memory_order_relaxed);
                    tiny_remote_watch_note("hot_remote_pending",
                                           h.ss,
                                           h.slab_idx,
                                           (void*)head,
                                           0xA251u,
                                           self_tid,
                                           0);
                }
                slab_release(&h);
            } else if (slab_is_safe_to_bind(&h)) {
                tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                tiny_sticky_save(class_idx, h.ss, h.slab_idx);
                ROUTE_MARK(8); ROUTE_COMMIT(class_idx, 0x04); return h.ss;
            } else {
                slab_release(&h);
            }
        }
        }
    }
    // Bench
    {
        ROUTE_MARK(9); // bench_try
        uintptr_t entb = bench_pub_pop(class_idx);
        if (entb) {
            SuperSlab* bss = slab_entry_ss(entb);
            int bidx = slab_entry_idx(entb);

            // Box: Try to acquire ownership
            SlabHandle h = slab_try_acquire(bss, bidx, self_tid);
        if (slab_is_valid(&h)) {
            if (slab_remote_pending(&h)) {
                slab_drain_remote_full(&h);
                if (__builtin_expect(g_debug_remote_guard, 0)) {
                    uintptr_t head = atomic_load_explicit(&h.ss->remote_heads[h.slab_idx], memory_order_relaxed);
                    tiny_remote_watch_note("bench_remote_pending",
                                           h.ss,
                                           h.slab_idx,
                                           (void*)head,
                                           0xA252u,
                                           self_tid,
                                           0);
                }
                slab_release(&h);
            } else if (slab_is_safe_to_bind(&h)) {
                tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                tiny_sticky_save(class_idx, h.ss, h.slab_idx);
                ROUTE_MARK(10); ROUTE_COMMIT(class_idx, 0x05); return h.ss;
            } else {
                slab_release(&h);
            }
        }
        }
    }
    // Mailbox (for non-hot classes)
    if (class_idx > 3) {
        ROUTE_MARK(3); // mail_try (non-hot)
        uintptr_t mail = tiny_mail_ready_allowed() ? mailbox_box_fetch(class_idx) : (uintptr_t)0;
        if (mail) {
            SuperSlab* mss = slab_entry_ss(mail);
            int midx = slab_entry_idx(mail);

            // Box: Try to acquire ownership
            SlabHandle h = slab_try_acquire(mss, midx, self_tid);
        if (slab_is_valid(&h)) {
            if (slab_remote_pending(&h)) {
                slab_drain_remote_full(&h);
                if (__builtin_expect(g_debug_remote_guard, 0)) {
                    uintptr_t head = atomic_load_explicit(&h.ss->remote_heads[h.slab_idx], memory_order_relaxed);
                    tiny_remote_watch_note("mailbox_remote_pending",
                                           h.ss,
                                           h.slab_idx,
                                           (void*)head,
                                           0xA253u,
                                           self_tid,
                                           0);
                }
                slab_release(&h);
            } else if (slab_is_safe_to_bind(&h)) {
                tiny_tls_bind_slab(tls, h.ss, h.slab_idx);
                tiny_sticky_save(class_idx, h.ss, h.slab_idx);
                ROUTE_MARK(4); ROUTE_COMMIT(class_idx, 0x02); return h.ss;
            } else {
                slab_release(&h);
            }
        }
        }
    }
    // Opportunistic background remote-drain (Box: Remote Drain Coalescer)
    // NOTE: BG Remote feature permanently disabled (dead code cleanup 2025-11-27)
    // This block was guarded by g_bg_remote_enable which defaulted to 0
    do {
        // Always skip - BG Remote feature removed
        break;

        // TLS miss tick per class
        static __thread unsigned miss_tick[8];
        unsigned t = ++miss_tick[class_idx];
        int period = tiny_bg_remote_tryrate();
        if (__builtin_expect(period <= 1 || (t % (unsigned)period) == 0, 0)) {
            int budget = tiny_bg_remote_budget_default();
            tiny_remote_bg_drain_step(class_idx, budget);
            // Quick second chance from Ready after drain
            uintptr_t ent2 = tiny_mail_ready_allowed() ? tiny_ready_pop(class_idx) : (uintptr_t)0;
            if (ent2) {
                SuperSlab* ss2 = slab_entry_ss(ent2);
                int idx2 = slab_entry_idx(ent2);
                uint32_t self_tid = tiny_self_u32();
                SlabHandle h2 = slab_try_acquire(ss2, idx2, self_tid);
                if (slab_is_valid(&h2)) {
                    if (slab_is_safe_to_bind(&h2)) {
                        tiny_tls_bind_slab(tls, h2.ss, h2.slab_idx);
                        tiny_sticky_save(class_idx, h2.ss, h2.slab_idx);
                        extern unsigned long long g_rf_hit_ready[];
                        g_rf_hit_ready[class_idx]++;
                        slab_release(&h2);
                        return h2.ss;
                    }
                    slab_release(&h2);
                }
            }
            // Ready Aggregator: peek mailbox and surface one hint into Ready
            do {
                const int agg_en = 0; // Ready aggregator ENV removed (fixed OFF)
                if (agg_en && tiny_mail_ready_allowed()) {
                    const int mb = 1;
                    tiny_ready_bg_aggregate_step(class_idx, mb);
                    uintptr_t ent3 = tiny_ready_pop(class_idx);
                    if (ent3) {
                        SuperSlab* ss3 = slab_entry_ss(ent3);
                        int idx3 = slab_entry_idx(ent3);
                        uint32_t self_tid = tiny_self_u32();
                        SlabHandle h3 = slab_try_acquire(ss3, idx3, self_tid);
                        if (slab_is_valid(&h3)) {
                            if (slab_is_safe_to_bind(&h3)) {
                                tiny_tls_bind_slab(tls, h3.ss, h3.slab_idx);
                                tiny_sticky_save(class_idx, h3.ss, h3.slab_idx);
                                extern unsigned long long g_rf_hit_ready[];
                                g_rf_hit_ready[class_idx]++;
                                slab_release(&h3);
                                return h3.ss;
                            }
                            slab_release(&h3);
                        }
                    }
                }
            } while (0);
        }
    } while (0);

    ROUTE_COMMIT(class_idx, 0xFF); // no candidate hit; fall back to slab/slow
    return NULL;
}