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gc.c
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gc.c
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#include <gc.h>
#include <stdbool.h>
#include <time.h>
#include "shapes.h"
#include "gc/objects.h"
#include "gc/refs.h"
#include "gc/strings.h"
#include "gc/ropes.h"
bool gc_disabled = false;
static size_t gc_tick = 0;
static uint64_t gc_last_run_ms = 0;
static size_t gc_nursery_threshold = GC_NURSERY_THRESHOLD;
static uint32_t gc_major_every_n = GC_MAJOR_EVERY_N_MINOR;
static uint32_t gc_major_live_growth_x256 = 384;
static uint32_t gc_major_pool_growth_x256 = 384;
static uint32_t gc_minor_surv_ewma = 128;
static uint32_t gc_major_recl_ewma = 26;
static uint64_t gc_now_ms(void) {
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return (uint64_t)ts.tv_sec * 1000ULL + (uint64_t)ts.tv_nsec / 1000000ULL;
}
static size_t gc_scaled_threshold(size_t base_live, uint32_t growth_x256, size_t floor) {
size_t scaled = (base_live * (size_t)growth_x256) / 256u;
if (scaled < floor) scaled = floor;
return scaled;
}
size_t gc_live_major_threshold(ant_t *js) {
size_t base_live = js ? js->gc_last_live : 0;
return gc_scaled_threshold(base_live, gc_major_live_growth_x256, 2048u);
}
size_t gc_pool_major_threshold(ant_t *js) {
size_t base_live = js ? js->gc_pool_last_live : 0;
return gc_scaled_threshold(base_live, gc_major_pool_growth_x256, 4u * 1024u * 1024u);
}
static void gc_adapt_nursery(size_t young_before, size_t survivors) {
if (young_before == 0) return;
uint32_t rate = (uint32_t)((survivors * 256) / young_before);
gc_minor_surv_ewma = (gc_minor_surv_ewma * 3 + rate) >> 2;
if (gc_minor_surv_ewma < 64 && gc_nursery_threshold > GC_NURSERY_THRESHOLD / 2)
gc_nursery_threshold -= gc_nursery_threshold / 4;
else if (gc_nursery_threshold < GC_NURSERY_THRESHOLD)
gc_nursery_threshold = GC_NURSERY_THRESHOLD;
}
static void gc_adapt_major_interval(size_t live_before, size_t live_after) {
if (live_before == 0) return;
size_t freed = live_before > live_after ? live_before - live_after : 0;
uint32_t rate = (uint32_t)((freed * 256) / live_before);
gc_major_recl_ewma = (gc_major_recl_ewma * 3 + rate) >> 2;
bool gen_ineffective = gc_minor_surv_ewma > 192; // >75% nursery survival
bool high_reclaim = gc_major_recl_ewma > 51; // >20% old-gen freed
bool low_reclaim = gc_major_recl_ewma < 13; // < 5% old-gen freed
if ((gen_ineffective && !low_reclaim) || high_reclaim) {
if (gc_major_every_n > 2) gc_major_every_n--;
} else if (!gen_ineffective && low_reclaim) {
if (gc_major_every_n < GC_MAJOR_EVERY_N_MINOR * 4) gc_major_every_n++;
}
if (gen_ineffective && low_reclaim) {
if (gc_major_live_growth_x256 < 1024) gc_major_live_growth_x256 += 96;
if (gc_major_pool_growth_x256 < 1536) gc_major_pool_growth_x256 += 128;
} else if (low_reclaim) {
if (gc_major_live_growth_x256 < 896) gc_major_live_growth_x256 += 48;
if (gc_major_pool_growth_x256 < 1280) gc_major_pool_growth_x256 += 64;
} else if (high_reclaim) {
if (gc_major_live_growth_x256 > 320) gc_major_live_growth_x256 -= 32;
if (gc_major_pool_growth_x256 > 320) gc_major_pool_growth_x256 -= 32;
} else {
if (gc_major_live_growth_x256 > 384) gc_major_live_growth_x256 -= 16;
else if (gc_major_live_growth_x256 < 384) gc_major_live_growth_x256 += 16;
if (gc_major_pool_growth_x256 > 384) gc_major_pool_growth_x256 -= 16;
else if (gc_major_pool_growth_x256 < 384) gc_major_pool_growth_x256 += 16;
}
}
static void gc_mark_str(ant_t *js, ant_value_t v) {
static const void *dispatch[] = {
[STR_HEAP_TAG_FLAT] = &&l_flat,
[STR_HEAP_TAG_ROPE] = &&l_rope,
[STR_HEAP_TAG_BUILDER] = &&l_builder,
};
if (v <= NANBOX_PREFIX) return;
uint8_t t = (v >> NANBOX_TYPE_SHIFT) & NANBOX_TYPE_MASK;
if (t != T_STR) return;
uintptr_t data = (uintptr_t)(v & NANBOX_DATA_MASK);
uintptr_t tag = data & STR_HEAP_TAG_MASK;
if (tag < sizeof(dispatch) / sizeof(*dispatch) && dispatch[tag])
goto *dispatch[tag];
goto l_flat;
l_rope: {
ant_rope_heap_t *rope = (ant_rope_heap_t *)(data & ~STR_HEAP_TAG_MASK);
if (!rope || !gc_ropes_mark(rope)) return;
gc_mark_str(js, rope->left);
gc_mark_str(js, rope->right);
gc_mark_str(js, rope->cached);
return;
}
l_builder: {
ant_string_builder_t *builder = (ant_string_builder_t *)(data & ~STR_HEAP_TAG_MASK);
if (!builder || !gc_ropes_mark(builder)) return;
gc_mark_value(js, builder->cached);
for (ant_builder_chunk_t *chunk = builder->head; chunk; chunk = chunk->next) {
if (gc_ropes_mark(chunk)) gc_mark_value(js, chunk->value);
}
return;
}
l_flat:
if (data) gc_strings_mark(js, (const void *)data);
return;
}
void gc_run(ant_t *js) {
if (__builtin_expect(gc_disabled, 0)) return;
size_t live_before = js->obj_arena.live_count;
js->prop_refs_len = 0;
gc_refs_shrink(js);
gc_strings_begin(js);
gc_ropes_begin(js);
gc_objects_run(js, gc_mark_str);
ant_ic_epoch_bump();
gc_strings_sweep(js);
gc_ropes_sweep(js);
js->gc_last_live = js->obj_arena.live_count;
js->old_live_count = js->obj_arena.live_count;
js->minor_gc_count = 0;
ant_string_pool_stats_t pool_stats = js_string_pool_stats(&js->pool.string);
js->gc_pool_last_live = pool_stats.total.used;
js->gc_pool_alloc = 0;
gc_adapt_major_interval(live_before, js->obj_arena.live_count);
gc_last_run_ms = gc_now_ms();
}
void gc_run_minor(ant_t *js) {
if (__builtin_expect(gc_disabled, 0)) return;
size_t old_before = js->old_live_count;
size_t live_before = js->obj_arena.live_count;
size_t young_before = live_before > old_before ? live_before - old_before : 0;
gc_objects_run_minor(js, NULL);
ant_ic_epoch_bump();
js->gc_last_live = js->obj_arena.live_count;
js->old_live_count = js->obj_arena.live_count;
js->minor_gc_count++;
size_t survivors = js->obj_arena.live_count > old_before
? js->obj_arena.live_count - old_before : 0;
gc_adapt_nursery(young_before, survivors);
gc_last_run_ms = gc_now_ms();
}
void gc_maybe(ant_t *js) {
if (__builtin_expect(gc_disabled, 0)) return;
if (++gc_tick < GC_MIN_TICK) return;
size_t live = js->obj_arena.live_count;
size_t young_count = live > js->old_live_count ? live - js->old_live_count : 0;
if (young_count >= gc_nursery_threshold) {
gc_tick = 0;
gc_run_minor(js);
if (js->minor_gc_count >= gc_major_every_n) {
js->minor_gc_count = 0;
gc_run(js);
}
return;
}
size_t threshold = gc_live_major_threshold(js);
if (live >= threshold) {
gc_tick = 0;
gc_run(js);
return;
}
if (gc_tick < 8192) return;
if (young_count == 0 && js->gc_pool_alloc == 0) {
gc_tick = 0;
return;
}
if (gc_now_ms() - gc_last_run_ms < GC_FORCE_INTERVAL_MS) {
gc_tick = 0;
return;
}
gc_tick = 0;
gc_run(js);
}

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