c9053a43ac
## Phase 6-2.3: Fix 4T Larson crash (active counter bug) ✅ **Problem:** 4T Larson crashed with "free(): invalid pointer", OOM errors **Root cause:** core/hakmem_tiny_refill_p0.inc.h:103 - P0 batch refill moved freelist blocks to TLS cache - Active counter NOT incremented → double-decrement on free - Counter underflows → SuperSlab appears full → OOM → crash **Fix:** Added ss_active_add(tls->ss, from_freelist); **Result:** 4T stable at 838K ops/s ✅ ## Phase 6-2.4: Fix SEGV in random_mixed/mid_large_mt benchmarks ✅ **Problem:** bench_random_mixed_hakmem, bench_mid_large_mt_hakmem → immediate SEGV **Root cause #1:** core/box/hak_free_api.inc.h:92-95 - "Guess loop" dereferenced unmapped memory when registry lookup failed **Root cause #2:** core/box/hak_free_api.inc.h:115 - Header magic check dereferenced unmapped memory **Fix:** 1. Removed dangerous guess loop (lines 92-95) 2. Added hak_is_memory_readable() check before dereferencing header (core/hakmem_internal.h:277-294 - uses mincore() syscall) **Result:** - random_mixed (2KB): SEGV → 2.22M ops/s ✅ - random_mixed (4KB): SEGV → 2.58M ops/s ✅ - Larson 4T: no regression (838K ops/s) ✅ ## Phase 6-2.5: Performance investigation + SuperSlab fix (WIP) ⚠️ **Problem:** Severe performance gaps (19-26x slower than system malloc) **Investigation:** Task agent identified root cause - hak_is_memory_readable() syscall overhead (100-300 cycles per free) - ALL frees hit unmapped_header_fallback path - SuperSlab lookup NEVER called - Why? g_use_superslab = 0 (disabled by diet mode) **Root cause:** core/hakmem_tiny_init.inc:104-105 - Diet mode (default ON) disables SuperSlab - SuperSlab defaults to 1 (hakmem_config.c:334) - BUT diet mode overrides it to 0 during init **Fix:** Separate SuperSlab from diet mode - SuperSlab: Performance-critical (fast alloc/free) - Diet mode: Memory efficiency (magazine capacity limits only) - Both are independent features, should not interfere **Status:** ⚠️ INCOMPLETE - New SEGV discovered after fix - SuperSlab lookup now works (confirmed via debug output) - But benchmark crashes (Exit 139) after ~20 lookups - Needs further investigation **Files modified:** - core/hakmem_tiny_init.inc:99-109 - Removed diet mode override - PERFORMANCE_INVESTIGATION_REPORT.md - Task agent analysis (303x instruction gap) **Next steps:** - Investigate new SEGV (likely SuperSlab free path bug) - OR: Revert Phase 6-2.5 changes if blocking progress 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
59 lines
2.4 KiB
C
59 lines
2.4 KiB
C
#include "free_local_box.h"
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#include "free_publish_box.h"
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#include "hakmem_tiny.h"
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void tiny_free_local_box(SuperSlab* ss, int slab_idx, TinySlabMeta* meta, void* ptr, uint32_t my_tid) {
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extern _Atomic uint64_t g_free_local_box_calls;
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atomic_fetch_add_explicit(&g_free_local_box_calls, 1, memory_order_relaxed);
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if (!(ss && ss->magic == SUPERSLAB_MAGIC)) return;
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if (slab_idx < 0 || slab_idx >= ss_slabs_capacity(ss)) return;
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(void)my_tid;
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if (__builtin_expect(tiny_refill_failfast_level() >= 2, 0)) {
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int actual_idx = slab_index_for(ss, ptr);
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if (actual_idx != slab_idx) {
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tiny_failfast_abort_ptr("free_local_box_idx", ss, slab_idx, ptr, "slab_idx_mismatch");
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} else {
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size_t blk = g_tiny_class_sizes[ss->size_class];
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uint8_t* slab_base = tiny_slab_base_for(ss, slab_idx);
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uintptr_t delta = (uintptr_t)ptr - (uintptr_t)slab_base;
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if (blk == 0 || (delta % blk) != 0) {
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tiny_failfast_abort_ptr("free_local_box_align", ss, slab_idx, ptr, "misaligned");
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} else if (meta && delta / blk >= meta->capacity) {
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tiny_failfast_abort_ptr("free_local_box_range", ss, slab_idx, ptr, "out_of_capacity");
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}
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}
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}
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void* prev = meta->freelist;
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*(void**)ptr = prev;
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meta->freelist = ptr;
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tiny_failfast_log("free_local_box", ss->size_class, ss, meta, ptr, prev);
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// BUGFIX: Memory barrier to ensure freelist visibility before used decrement
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// Without this, other threads can see new freelist but old used count (race)
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atomic_thread_fence(memory_order_release);
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// Optional freelist mask update on first push
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do {
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static int g_mask_en = -1;
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if (__builtin_expect(g_mask_en == -1, 0)) {
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const char* e = getenv("HAKMEM_TINY_FREELIST_MASK");
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g_mask_en = (e && *e && *e != '0') ? 1 : 0;
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}
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if (__builtin_expect(g_mask_en, 0) && prev == NULL) {
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uint32_t bit = (1u << slab_idx);
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atomic_fetch_or_explicit(&ss->freelist_mask, bit, memory_order_release);
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}
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} while (0);
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// Track local free (debug helpers may be no-op)
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tiny_remote_track_on_local_free(ss, slab_idx, ptr, "local_free", my_tid);
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meta->used--;
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ss_active_dec_one(ss);
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if (prev == NULL) {
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// First-free → advertise slab to adopters
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tiny_free_publish_first_free((int)ss->size_class, ss, slab_idx);
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}
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}
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