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guile/libguile/whippet/src/mmc.c

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#include <pthread.h>
#include <stdatomic.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "gc-api.h"
#define GC_IMPL 1
#include "gc-internal.h"
#include "background-thread.h"
#include "debug.h"
#include "field-set.h"
#include "gc-align.h"
#include "gc-inline.h"
#include "gc-platform.h"
#include "gc-stack.h"
#include "gc-trace.h"
#include "gc-tracepoint.h"
#include "heap-sizer.h"
#include "large-object-space.h"
#include "nofl-space.h"
#if GC_PARALLEL
#include "parallel-tracer.h"
#else
#include "serial-tracer.h"
#endif
#include "spin.h"
#include "mmc-attrs.h"
#define LARGE_OBJECT_THRESHOLD 8192
struct gc_heap {
struct nofl_space nofl_space;
struct large_object_space large_object_space;
struct gc_extern_space *extern_space;
struct gc_field_set remembered_set;
size_t large_object_pages;
pthread_mutex_t lock;
pthread_cond_t collector_cond;
pthread_cond_t mutator_cond;
size_t size;
size_t total_allocated_bytes_at_last_gc;
size_t size_at_last_gc;
int collecting;
int check_pending_ephemerons;
struct gc_pending_ephemerons *pending_ephemerons;
struct gc_finalizer_state *finalizer_state;
enum gc_collection_kind gc_kind;
size_t mutator_count;
size_t paused_mutator_count;
size_t inactive_mutator_count;
struct gc_heap_roots *roots;
struct gc_mutator *mutators;
long count;
struct gc_tracer tracer;
double fragmentation_low_threshold;
double fragmentation_high_threshold;
double minor_gc_yield_threshold;
double major_gc_yield_threshold;
double minimum_major_gc_yield_threshold;
double pending_ephemerons_size_factor;
double pending_ephemerons_size_slop;
struct gc_background_thread *background_thread;
struct gc_heap_sizer sizer;
struct gc_event_listener event_listener;
void *event_listener_data;
void* (*allocation_failure)(struct gc_heap*, size_t);
};
#define HEAP_EVENT(heap, event, ...) do { \
(heap)->event_listener.event((heap)->event_listener_data, ##__VA_ARGS__); \
GC_TRACEPOINT(event, ##__VA_ARGS__); \
} while (0)
#define MUTATOR_EVENT(mut, event, ...) do { \
(mut)->heap->event_listener.event((mut)->event_listener_data, \
##__VA_ARGS__); \
GC_TRACEPOINT(event, ##__VA_ARGS__); \
} while (0)
struct gc_mutator {
struct nofl_allocator allocator;
struct gc_field_set_writer logger;
struct gc_heap *heap;
struct gc_stack stack;
struct gc_mutator_roots *roots;
void *event_listener_data;
struct gc_mutator *next;
struct gc_mutator *prev;
};
struct gc_trace_worker_data {
struct nofl_allocator allocator;
};
static inline struct nofl_space*
heap_nofl_space(struct gc_heap *heap) {
return &heap->nofl_space;
}
static inline struct large_object_space*
heap_large_object_space(struct gc_heap *heap) {
return &heap->large_object_space;
}
static inline struct gc_extern_space*
heap_extern_space(struct gc_heap *heap) {
return heap->extern_space;
}
static inline struct gc_heap*
mutator_heap(struct gc_mutator *mutator) {
return mutator->heap;
}
struct gc_heap* gc_mutator_heap(struct gc_mutator *mutator) {
return mutator_heap(mutator);
}
uintptr_t gc_small_object_nursery_low_address(struct gc_heap *heap) {
GC_CRASH();
}
uintptr_t gc_small_object_nursery_high_address(struct gc_heap *heap) {
GC_CRASH();
}
static void
gc_trace_worker_call_with_data(void (*f)(struct gc_tracer *tracer,
struct gc_heap *heap,
struct gc_trace_worker *worker,
struct gc_trace_worker_data *data),
struct gc_tracer *tracer,
struct gc_heap *heap,
struct gc_trace_worker *worker) {
struct gc_trace_worker_data data;
nofl_allocator_reset(&data.allocator);
f(tracer, heap, worker, &data);
nofl_allocator_finish(&data.allocator, heap_nofl_space(heap));
}
static inline int
do_trace(struct gc_heap *heap, struct gc_edge edge, struct gc_ref ref,
struct gc_trace_worker_data *data) {
if (GC_LIKELY(nofl_space_contains(heap_nofl_space(heap), ref)))
return nofl_space_evacuate_or_mark_object(heap_nofl_space(heap), edge, ref,
&data->allocator);
else if (large_object_space_contains_with_lock(heap_large_object_space(heap), ref))
return large_object_space_mark(heap_large_object_space(heap), ref);
else
return gc_extern_space_visit(heap_extern_space(heap), edge, ref);
}
static inline int
trace_edge(struct gc_heap *heap, struct gc_edge edge,
struct gc_trace_worker_data *data) {
struct gc_ref ref = gc_edge_ref(edge);
if (gc_ref_is_null(ref) || gc_ref_is_immediate(ref))
return 0;
int is_new = do_trace(heap, edge, ref, data);
if (is_new &&
GC_UNLIKELY(atomic_load_explicit(&heap->check_pending_ephemerons,
memory_order_relaxed)))
gc_resolve_pending_ephemerons(ref, heap);
return is_new;
}
int
gc_visit_ephemeron_key(struct gc_edge edge, struct gc_heap *heap) {
struct gc_ref ref = gc_edge_ref(edge);
GC_ASSERT(!gc_ref_is_null(ref));
if (gc_ref_is_immediate(ref))
return 1;
GC_ASSERT(gc_ref_is_heap_object(ref));
struct nofl_space *nofl_space = heap_nofl_space(heap);
if (GC_LIKELY(nofl_space_contains(nofl_space, ref)))
return nofl_space_forward_or_mark_if_traced(nofl_space, edge, ref);
struct large_object_space *lospace = heap_large_object_space(heap);
if (large_object_space_contains_with_lock(lospace, ref))
return large_object_space_is_marked(lospace, ref);
GC_CRASH();
}
static int
mutators_are_stopping(struct gc_heap *heap) {
return atomic_load_explicit(&heap->collecting, memory_order_relaxed);
}
static inline void
heap_lock(struct gc_heap *heap) {
pthread_mutex_lock(&heap->lock);
}
static inline void
heap_unlock(struct gc_heap *heap) {
pthread_mutex_unlock(&heap->lock);
}
// with heap lock
static inline int
all_mutators_stopped(struct gc_heap *heap) {
return heap->mutator_count ==
heap->paused_mutator_count + heap->inactive_mutator_count;
}
static void
add_mutator(struct gc_heap *heap, struct gc_mutator *mut) {
mut->heap = heap;
mut->event_listener_data =
heap->event_listener.mutator_added(heap->event_listener_data);
nofl_allocator_reset(&mut->allocator);
gc_field_set_writer_init(&mut->logger, &heap->remembered_set);
heap_lock(heap);
// We have no roots. If there is a GC currently in progress, we have
// nothing to add. Just wait until it's done.
while (mutators_are_stopping(heap))
pthread_cond_wait(&heap->mutator_cond, &heap->lock);
mut->next = mut->prev = NULL;
struct gc_mutator *tail = heap->mutators;
if (tail) {
mut->next = tail;
tail->prev = mut;
}
heap->mutators = mut;
heap->mutator_count++;
heap_unlock(heap);
}
static void
remove_mutator(struct gc_heap *heap, struct gc_mutator *mut) {
nofl_allocator_finish(&mut->allocator, heap_nofl_space(heap));
if (GC_GENERATIONAL)
gc_field_set_writer_release_buffer(&mut->logger);
MUTATOR_EVENT(mut, mutator_removed);
mut->heap = NULL;
heap_lock(heap);
heap->mutator_count--;
if (mut->next)
mut->next->prev = mut->prev;
if (mut->prev)
mut->prev->next = mut->next;
else
heap->mutators = mut->next;
// We have no roots. If there is a GC stop currently in progress,
// maybe tell the controller it can continue.
if (mutators_are_stopping(heap) && all_mutators_stopped(heap))
pthread_cond_signal(&heap->collector_cond);
heap_unlock(heap);
}
void
gc_mutator_set_roots(struct gc_mutator *mut, struct gc_mutator_roots *roots) {
mut->roots = roots;
}
void
gc_heap_set_roots(struct gc_heap *heap, struct gc_heap_roots *roots) {
heap->roots = roots;
}
void
gc_heap_set_extern_space(struct gc_heap *heap, struct gc_extern_space *space) {
heap->extern_space = space;
}
static inline void tracer_visit(struct gc_edge edge, struct gc_heap *heap,
void *trace_data) GC_ALWAYS_INLINE;
static inline void
tracer_visit(struct gc_edge edge, struct gc_heap *heap, void *trace_data) {
struct gc_trace_worker *worker = trace_data;
if (trace_edge(heap, edge, gc_trace_worker_data(worker)))
gc_trace_worker_enqueue(worker, gc_edge_ref(edge));
}
static inline int
trace_remembered_edge(struct gc_edge edge, struct gc_heap *heap, void *trace_data) {
tracer_visit(edge, heap, trace_data);
// Keep the edge in the remembered set; we clear these in bulk later.
return 1;
}
static inline struct gc_ref
do_trace_conservative_ref(struct gc_heap *heap, struct gc_conservative_ref ref,
int possibly_interior) {
if (!gc_conservative_ref_might_be_a_heap_object(ref, possibly_interior))
return gc_ref_null();
struct nofl_space *nofl_space = heap_nofl_space(heap);
if (GC_LIKELY(nofl_space_contains_conservative_ref(nofl_space, ref)))
return nofl_space_mark_conservative_ref(nofl_space, ref, possibly_interior);
struct large_object_space *lospace = heap_large_object_space(heap);
return large_object_space_mark_conservative_ref(lospace, ref,
possibly_interior);
}
static inline struct gc_ref
trace_conservative_ref(struct gc_heap *heap, struct gc_conservative_ref ref,
int possibly_interior) {
struct gc_ref ret = do_trace_conservative_ref(heap, ref, possibly_interior);
if (!gc_ref_is_null(ret)) {
if (GC_UNLIKELY(atomic_load_explicit(&heap->check_pending_ephemerons,
memory_order_relaxed)))
gc_resolve_pending_ephemerons(ret, heap);
}
return ret;
}
static inline void
tracer_trace_conservative_ref(struct gc_conservative_ref ref,
struct gc_heap *heap,
struct gc_trace_worker *worker,
int possibly_interior) {
struct gc_ref resolved = trace_conservative_ref(heap, ref, possibly_interior);
if (!gc_ref_is_null(resolved))
gc_trace_worker_enqueue(worker, resolved);
}
static inline struct gc_conservative_ref
load_conservative_ref(uintptr_t addr) {
GC_ASSERT((addr & (sizeof(uintptr_t) - 1)) == 0);
uintptr_t val;
memcpy(&val, (char*)addr, sizeof(uintptr_t));
return gc_conservative_ref(val);
}
static inline void
trace_conservative_edges(uintptr_t low, uintptr_t high, int possibly_interior,
struct gc_heap *heap, struct gc_trace_worker *worker) {
GC_ASSERT(low == align_down(low, sizeof(uintptr_t)));
GC_ASSERT(high == align_down(high, sizeof(uintptr_t)));
for (uintptr_t addr = low; addr < high; addr += sizeof(uintptr_t))
tracer_trace_conservative_ref(load_conservative_ref(addr), heap, worker,
possibly_interior);
}
static inline struct gc_trace_plan
trace_plan(struct gc_heap *heap, struct gc_ref ref) {
if (GC_LIKELY(nofl_space_contains(heap_nofl_space(heap), ref))) {
return nofl_space_object_trace_plan(heap_nofl_space(heap), ref);
} else {
return large_object_space_object_trace_plan(heap_large_object_space(heap),
ref);
}
}
static inline void
trace_one(struct gc_ref ref, struct gc_heap *heap,
struct gc_trace_worker *worker) {
struct gc_trace_plan plan = trace_plan(heap, ref);
switch (plan.kind) {
case GC_TRACE_PRECISELY:
gc_trace_object(ref, tracer_visit, heap, worker, NULL);
break;
case GC_TRACE_NONE:
break;
case GC_TRACE_CONSERVATIVELY: {
// Intraheap edges are not interior.
uintptr_t addr = gc_ref_value(ref);
int possibly_interior = 0;
trace_conservative_edges(addr, addr + plan.size, possibly_interior,
heap, worker);
break;
}
case GC_TRACE_EPHEMERON:
gc_trace_ephemeron(gc_ref_heap_object(ref), tracer_visit, heap,
worker);
break;
default:
GC_CRASH();
}
}
static inline void
trace_root(struct gc_root root, struct gc_heap *heap,
struct gc_trace_worker *worker) {
switch (root.kind) {
case GC_ROOT_KIND_HEAP:
gc_trace_heap_roots(root.heap->roots, tracer_visit, heap, worker);
break;
case GC_ROOT_KIND_MUTATOR:
gc_trace_mutator_roots(root.mutator->roots, tracer_visit, heap, worker);
break;
case GC_ROOT_KIND_CONSERVATIVE_EDGES:
trace_conservative_edges(root.range.lo_addr, root.range.hi_addr, 0,
heap, worker);
break;
case GC_ROOT_KIND_CONSERVATIVE_POSSIBLY_INTERIOR_EDGES:
trace_conservative_edges(root.range.lo_addr, root.range.hi_addr, 1,
heap, worker);
break;
case GC_ROOT_KIND_RESOLVED_EPHEMERONS:
gc_trace_resolved_ephemerons(root.resolved_ephemerons, tracer_visit,
heap, worker);
break;
case GC_ROOT_KIND_EDGE:
tracer_visit(root.edge, heap, worker);
break;
case GC_ROOT_KIND_EDGE_BUFFER:
gc_field_set_visit_edge_buffer(&heap->remembered_set, root.edge_buffer,
trace_remembered_edge, heap, worker);
break;
default:
GC_CRASH();
}
}
static void
request_mutators_to_stop(struct gc_heap *heap) {
GC_ASSERT(!mutators_are_stopping(heap));
atomic_store_explicit(&heap->collecting, 1, memory_order_relaxed);
}
static void
allow_mutators_to_continue(struct gc_heap *heap) {
GC_ASSERT(mutators_are_stopping(heap));
GC_ASSERT(all_mutators_stopped(heap));
heap->paused_mutator_count--;
atomic_store_explicit(&heap->collecting, 0, memory_order_relaxed);
GC_ASSERT(!mutators_are_stopping(heap));
pthread_cond_broadcast(&heap->mutator_cond);
}
static void
heap_reset_large_object_pages(struct gc_heap *heap, size_t npages) {
size_t previous = heap->large_object_pages;
heap->large_object_pages = npages;
GC_ASSERT(npages <= previous);
size_t bytes = (previous - npages) <<
heap_large_object_space(heap)->page_size_log2;
// If heap size is fixed, we won't need to allocate any more nofl blocks, as
// nothing uses paged-out blocks except large object allocation. But if the
// heap can grow, growth can consume nofl-space blocks that were paged out to
// allow for lospace allocations, which means that here we may need to
// allocate additional slabs.
nofl_space_expand(heap_nofl_space(heap), bytes);
}
static void
wait_for_mutators_to_stop(struct gc_heap *heap) {
heap->paused_mutator_count++;
while (!all_mutators_stopped(heap))
pthread_cond_wait(&heap->collector_cond, &heap->lock);
}
static enum gc_collection_kind
pause_mutator_for_collection(struct gc_heap *heap,
struct gc_mutator *mut) GC_NEVER_INLINE;
static enum gc_collection_kind
pause_mutator_for_collection(struct gc_heap *heap, struct gc_mutator *mut) {
GC_ASSERT(mutators_are_stopping(heap));
GC_ASSERT(!all_mutators_stopped(heap));
MUTATOR_EVENT(mut, mutator_stopping);
MUTATOR_EVENT(mut, mutator_stopped);
heap->paused_mutator_count++;
enum gc_collection_kind collection_kind = heap->gc_kind;
if (all_mutators_stopped(heap))
pthread_cond_signal(&heap->collector_cond);
do
pthread_cond_wait(&heap->mutator_cond, &heap->lock);
while (mutators_are_stopping(heap));
heap->paused_mutator_count--;
MUTATOR_EVENT(mut, mutator_restarted);
return collection_kind;
}
static void
resize_heap(struct gc_heap *heap, size_t new_size) {
if (new_size == heap->size)
return;
DEBUG("------ resizing heap\n");
DEBUG("------ old heap size: %zu bytes\n", heap->size);
DEBUG("------ new heap size: %zu bytes\n", new_size);
if (new_size < heap->size)
nofl_space_shrink(heap_nofl_space(heap), heap->size - new_size);
else
nofl_space_expand(heap_nofl_space(heap), new_size - heap->size);
heap->size = new_size;
HEAP_EVENT(heap, heap_resized, new_size);
}
static double
heap_last_gc_yield(struct gc_heap *heap) {
size_t live_size =
nofl_space_live_size_at_last_collection(heap_nofl_space(heap)) +
large_object_space_size_at_last_collection(heap_large_object_space(heap));
if (live_size > heap->size_at_last_gc)
return 0;
return 1.0 - ((double) live_size) / heap->size_at_last_gc;
}
static double
heap_fragmentation(struct gc_heap *heap) {
struct nofl_space *nofl_space = heap_nofl_space(heap);
size_t fragmentation = nofl_space_fragmentation(nofl_space);
return ((double)fragmentation) / heap->size;
}
static size_t
heap_estimate_live_data_after_gc(struct gc_heap *heap,
size_t last_live_bytes,
double last_yield) {
size_t bytes =
nofl_space_estimate_live_bytes_after_gc(heap_nofl_space(heap),
last_yield)
+ large_object_space_size_at_last_collection(heap_large_object_space(heap));
if (bytes < last_live_bytes)
return last_live_bytes;
return bytes;
}
static int
compute_progress(struct gc_heap *heap, uintptr_t allocation_since_last_gc) {
struct nofl_space *nofl = heap_nofl_space(heap);
return allocation_since_last_gc > nofl_space_fragmentation(nofl);
}
static int
compute_success(struct gc_heap *heap, enum gc_collection_kind gc_kind,
int progress) {
return progress
|| gc_kind == GC_COLLECTION_MINOR
|| heap->sizer.policy != GC_HEAP_SIZE_FIXED;
}
static double
clamp_major_gc_yield_threshold(struct gc_heap *heap, double threshold) {
if (threshold < heap->minimum_major_gc_yield_threshold)
threshold = heap->minimum_major_gc_yield_threshold;
double one_block = NOFL_BLOCK_SIZE * 1.0 / heap->size;
if (threshold < one_block)
threshold = one_block;
return threshold;
}
static enum gc_collection_kind
determine_collection_kind(struct gc_heap *heap,
enum gc_collection_kind requested) {
struct nofl_space *nofl_space = heap_nofl_space(heap);
enum gc_collection_kind previous_gc_kind = atomic_load(&heap->gc_kind);
enum gc_collection_kind gc_kind;
double yield = heap_last_gc_yield(heap);
double fragmentation = heap_fragmentation(heap);
ssize_t pending = atomic_load_explicit(&nofl_space->pending_unavailable_bytes,
memory_order_acquire);
if (heap->count == 0) {
DEBUG("first collection is always major\n");
gc_kind = GC_COLLECTION_MAJOR;
} else if (requested != GC_COLLECTION_ANY) {
DEBUG("user specifically requested collection kind %d\n", (int)requested);
gc_kind = requested;
} else if (pending > 0) {
DEBUG("evacuating due to need to reclaim %zd bytes\n", pending);
// During the last cycle, a large allocation could not find enough
// free blocks, and we decided not to expand the heap. Let's do an
// evacuating major collection to maximize the free block yield.
gc_kind = GC_COLLECTION_COMPACTING;
} else if (previous_gc_kind == GC_COLLECTION_COMPACTING
&& fragmentation >= heap->fragmentation_low_threshold) {
DEBUG("continuing evacuation due to fragmentation %.2f%% > %.2f%%\n",
fragmentation * 100.,
heap->fragmentation_low_threshold * 100.);
// For some reason, we already decided to compact in the past,
// and fragmentation hasn't yet fallen below a low-water-mark.
// Keep going.
gc_kind = GC_COLLECTION_COMPACTING;
} else if (fragmentation > heap->fragmentation_high_threshold) {
// Switch to evacuation mode if the heap is too fragmented.
DEBUG("triggering compaction due to fragmentation %.2f%% > %.2f%%\n",
fragmentation * 100.,
heap->fragmentation_high_threshold * 100.);
gc_kind = GC_COLLECTION_COMPACTING;
} else if (previous_gc_kind == GC_COLLECTION_COMPACTING) {
// We were evacuating, but we're good now. Go back to minor
// collections.
DEBUG("returning to in-place collection, fragmentation %.2f%% < %.2f%%\n",
fragmentation * 100.,
heap->fragmentation_low_threshold * 100.);
gc_kind = GC_GENERATIONAL ? GC_COLLECTION_MINOR : GC_COLLECTION_MAJOR;
} else if (!GC_GENERATIONAL) {
DEBUG("keeping on with major in-place GC\n");
GC_ASSERT(previous_gc_kind == GC_COLLECTION_MAJOR);
gc_kind = GC_COLLECTION_MAJOR;
} else if (previous_gc_kind != GC_COLLECTION_MINOR) {
DEBUG("returning to minor collection\n");
// Go back to minor collections.
gc_kind = GC_COLLECTION_MINOR;
} else if (yield < heap->major_gc_yield_threshold) {
DEBUG("collection yield too low, triggering major collection\n");
// Nursery is getting tight; trigger a major GC.
gc_kind = GC_COLLECTION_MAJOR;
} else {
DEBUG("keeping on with minor GC\n");
// Nursery has adequate space; keep trucking with minor GCs.
GC_ASSERT(previous_gc_kind == GC_COLLECTION_MINOR);
gc_kind = GC_COLLECTION_MINOR;
}
if (gc_has_conservative_intraheap_edges() &&
gc_kind == GC_COLLECTION_COMPACTING) {
DEBUG("welp. conservative heap scanning, no evacuation for you\n");
gc_kind = GC_COLLECTION_MAJOR;
}
// If this is the first in a series of minor collections, reset the
// threshold at which we should do a major GC.
if (gc_kind == GC_COLLECTION_MINOR &&
previous_gc_kind != GC_COLLECTION_MINOR) {
double yield = heap_last_gc_yield(heap);
double threshold = yield * heap->minor_gc_yield_threshold;
double clamped = clamp_major_gc_yield_threshold(heap, threshold);
heap->major_gc_yield_threshold = clamped;
DEBUG("first minor collection at yield %.2f%%, threshold %.2f%%\n",
yield * 100., clamped * 100.);
}
atomic_store(&heap->gc_kind, gc_kind);
return gc_kind;
}
static void
enqueue_conservative_roots(uintptr_t low, uintptr_t high,
struct gc_heap *heap, void *data) {
int *possibly_interior = data;
gc_tracer_add_root(&heap->tracer,
gc_root_conservative_edges(low, high, *possibly_interior));
}
static int
enqueue_mutator_conservative_roots(struct gc_heap *heap) {
if (gc_has_mutator_conservative_roots()) {
int possibly_interior = gc_mutator_conservative_roots_may_be_interior();
for (struct gc_mutator *mut = heap->mutators;
mut;
mut = mut->next)
gc_stack_visit(&mut->stack, enqueue_conservative_roots, heap,
&possibly_interior);
return 1;
}
return 0;
}
static int
enqueue_global_conservative_roots(struct gc_heap *heap) {
if (gc_has_global_conservative_roots()) {
int possibly_interior = 0;
gc_platform_visit_global_conservative_roots
(enqueue_conservative_roots, heap, &possibly_interior);
return 1;
}
return 0;
}
static int
enqueue_pinned_roots(struct gc_heap *heap) {
GC_ASSERT(!heap_nofl_space(heap)->evacuating);
int has_pinned_roots = enqueue_mutator_conservative_roots(heap);
has_pinned_roots |= enqueue_global_conservative_roots(heap);
return has_pinned_roots;
}
static void
enqueue_root_edge(struct gc_edge edge, struct gc_heap *heap, void *unused) {
gc_tracer_add_root(&heap->tracer, gc_root_edge(edge));
}
static void
enqueue_generational_roots(struct gc_heap *heap,
enum gc_collection_kind gc_kind) {
if (!GC_GENERATIONAL) return;
if (gc_kind == GC_COLLECTION_MINOR)
gc_field_set_add_roots(&heap->remembered_set, &heap->tracer);
}
static inline void
forget_remembered_edge(struct gc_edge edge, struct gc_heap *heap) {
struct nofl_space *space = heap_nofl_space(heap);
if (nofl_space_contains_edge(space, edge))
nofl_space_forget_edge(space, edge);
// Otherwise the edge is in the lospace, whose remembered edges are
// cleared in bulk.
}
static void
clear_remembered_set(struct gc_heap *heap) {
if (!GC_GENERATIONAL) return;
gc_field_set_clear(&heap->remembered_set, forget_remembered_edge, heap);
large_object_space_clear_remembered_edges(heap_large_object_space(heap));
}
static void
enqueue_relocatable_roots(struct gc_heap *heap,
enum gc_collection_kind gc_kind) {
for (struct gc_mutator *mut = heap->mutators;
mut;
mut = mut->next) {
if (mut->roots)
gc_tracer_add_root(&heap->tracer, gc_root_mutator(mut));
}
if (heap->roots)
gc_tracer_add_root(&heap->tracer, gc_root_heap(heap));
gc_visit_finalizer_roots(heap->finalizer_state, enqueue_root_edge, heap, NULL);
enqueue_generational_roots(heap, gc_kind);
}
static void
resolve_ephemerons_lazily(struct gc_heap *heap) {
atomic_store_explicit(&heap->check_pending_ephemerons, 0,
memory_order_release);
}
static void
resolve_ephemerons_eagerly(struct gc_heap *heap) {
atomic_store_explicit(&heap->check_pending_ephemerons, 1,
memory_order_release);
gc_scan_pending_ephemerons(heap->pending_ephemerons, heap, 0, 1);
}
static void
trace_resolved_ephemerons(struct gc_heap *heap) {
for (struct gc_ephemeron *resolved = gc_pop_resolved_ephemerons(heap);
resolved;
resolved = gc_pop_resolved_ephemerons(heap)) {
gc_tracer_add_root(&heap->tracer, gc_root_resolved_ephemerons(resolved));
gc_tracer_trace(&heap->tracer);
}
}
static void
resolve_finalizers(struct gc_heap *heap) {
for (size_t priority = 0;
priority < gc_finalizer_priority_count();
priority++) {
if (gc_resolve_finalizers(heap->finalizer_state, priority,
enqueue_root_edge, heap, NULL)) {
gc_tracer_trace(&heap->tracer);
trace_resolved_ephemerons(heap);
}
}
gc_notify_finalizers(heap->finalizer_state, heap);
}
static void
sweep_ephemerons(struct gc_heap *heap) {
return gc_sweep_pending_ephemerons(heap->pending_ephemerons, 0, 1);
}
static int collect(struct gc_mutator *mut,
enum gc_collection_kind requested_kind) GC_NEVER_INLINE;
static int
collect(struct gc_mutator *mut, enum gc_collection_kind requested_kind) {
struct gc_heap *heap = mutator_heap(mut);
struct nofl_space *nofl_space = heap_nofl_space(heap);
struct large_object_space *lospace = heap_large_object_space(heap);
struct gc_extern_space *exspace = heap_extern_space(heap);
uint64_t start_ns = gc_platform_monotonic_nanoseconds();
MUTATOR_EVENT(mut, mutator_cause_gc);
DEBUG("start collect #%ld:\n", heap->count);
HEAP_EVENT(heap, requesting_stop);
request_mutators_to_stop(heap);
nofl_finish_sweeping(&mut->allocator, nofl_space);
HEAP_EVENT(heap, waiting_for_stop);
wait_for_mutators_to_stop(heap);
HEAP_EVENT(heap, mutators_stopped);
uint64_t allocation_counter = 0;
nofl_space_add_to_allocation_counter(nofl_space, &allocation_counter);
large_object_space_add_to_allocation_counter(lospace, &allocation_counter);
heap->total_allocated_bytes_at_last_gc += allocation_counter;
int progress = compute_progress(heap, allocation_counter);
enum gc_collection_kind gc_kind =
determine_collection_kind(heap, requested_kind);
int is_minor = gc_kind == GC_COLLECTION_MINOR;
HEAP_EVENT(heap, prepare_gc, gc_kind);
nofl_space_prepare_gc(nofl_space, gc_kind);
large_object_space_start_gc(lospace, is_minor);
gc_extern_space_start_gc(exspace, is_minor);
resolve_ephemerons_lazily(heap);
gc_tracer_prepare(&heap->tracer);
double yield = heap_last_gc_yield(heap);
double fragmentation = heap_fragmentation(heap);
size_t live_bytes = heap->size * (1.0 - yield);
HEAP_EVENT(heap, live_data_size, live_bytes);
DEBUG("last gc yield: %f; fragmentation: %f\n", yield, fragmentation);
// Eagerly trace pinned roots if we are going to relocate objects.
if (enqueue_pinned_roots(heap) && gc_kind == GC_COLLECTION_COMPACTING)
gc_tracer_trace_roots(&heap->tracer);
// Process the rest of the roots in parallel. This heap event should probably
// be removed, as there is no clear cutoff time.
HEAP_EVENT(heap, roots_traced);
enqueue_relocatable_roots(heap, gc_kind);
nofl_space_start_gc(nofl_space, gc_kind);
gc_tracer_trace(&heap->tracer);
HEAP_EVENT(heap, heap_traced);
resolve_ephemerons_eagerly(heap);
trace_resolved_ephemerons(heap);
HEAP_EVENT(heap, ephemerons_traced);
resolve_finalizers(heap);
HEAP_EVENT(heap, finalizers_traced);
sweep_ephemerons(heap);
gc_tracer_release(&heap->tracer);
clear_remembered_set(heap);
nofl_space_finish_gc(nofl_space, gc_kind);
large_object_space_finish_gc(lospace, is_minor);
gc_extern_space_finish_gc(exspace, is_minor);
heap->count++;
heap_reset_large_object_pages(heap, lospace->live_pages_at_last_collection);
uint64_t pause_ns = gc_platform_monotonic_nanoseconds() - start_ns;
size_t live_bytes_estimate =
heap_estimate_live_data_after_gc(heap, live_bytes, yield);
DEBUG("--- total live bytes estimate: %zu\n", live_bytes_estimate);
gc_heap_sizer_on_gc(heap->sizer, heap->size, live_bytes_estimate, pause_ns,
resize_heap);
heap->size_at_last_gc = heap->size;
HEAP_EVENT(heap, restarting_mutators);
allow_mutators_to_continue(heap);
return compute_success(heap, gc_kind, progress);
}
static int
trigger_collection(struct gc_mutator *mut,
enum gc_collection_kind requested_kind) {
struct gc_heap *heap = mutator_heap(mut);
int prev_kind = -1;
gc_stack_capture_hot(&mut->stack);
nofl_allocator_finish(&mut->allocator, heap_nofl_space(heap));
if (GC_GENERATIONAL)
gc_field_set_writer_release_buffer(&mut->logger);
heap_lock(heap);
while (mutators_are_stopping(heap))
prev_kind = pause_mutator_for_collection(heap, mut);
int success = 1;
if (prev_kind < (int)requested_kind)
success = collect(mut, requested_kind);
heap_unlock(heap);
return success;
}
void
gc_collect(struct gc_mutator *mut, enum gc_collection_kind kind) {
trigger_collection(mut, kind);
}
int*
gc_safepoint_flag_loc(struct gc_mutator *mut) {
return &mutator_heap(mut)->collecting;
}
void
gc_safepoint_slow(struct gc_mutator *mut) {
struct gc_heap *heap = mutator_heap(mut);
gc_stack_capture_hot(&mut->stack);
nofl_allocator_finish(&mut->allocator, heap_nofl_space(heap));
if (GC_GENERATIONAL)
gc_field_set_writer_release_buffer(&mut->logger);
heap_lock(heap);
while (mutators_are_stopping(mutator_heap(mut)))
pause_mutator_for_collection(heap, mut);
heap_unlock(heap);
}
static enum gc_trace_kind
compute_trace_kind(enum gc_allocation_kind kind) {
if (GC_CONSERVATIVE_TRACE) {
switch (kind) {
case GC_ALLOCATION_TAGGED:
case GC_ALLOCATION_UNTAGGED_CONSERVATIVE:
return GC_TRACE_CONSERVATIVELY;
case GC_ALLOCATION_TAGGED_POINTERLESS:
case GC_ALLOCATION_UNTAGGED_POINTERLESS:
return GC_TRACE_NONE;
default:
GC_CRASH();
};
} else {
switch (kind) {
case GC_ALLOCATION_TAGGED:
return GC_TRACE_PRECISELY;
case GC_ALLOCATION_TAGGED_POINTERLESS:
case GC_ALLOCATION_UNTAGGED_POINTERLESS:
return GC_TRACE_NONE;
case GC_ALLOCATION_UNTAGGED_CONSERVATIVE:
default:
GC_CRASH();
};
}
}
static void*
allocate_large(struct gc_mutator *mut, size_t size,
enum gc_trace_kind kind) {
struct gc_heap *heap = mutator_heap(mut);
struct nofl_space *nofl_space = heap_nofl_space(heap);
struct large_object_space *lospace = heap_large_object_space(heap);
size_t npages = large_object_space_npages(lospace, size);
nofl_space_request_release_memory(nofl_space,
npages << lospace->page_size_log2);
while (!nofl_space_shrink(nofl_space, 0)) {
if (!trigger_collection(mut, GC_COLLECTION_COMPACTING))
return heap->allocation_failure(heap, size);
}
atomic_fetch_add(&heap->large_object_pages, npages);
void *ret = large_object_space_alloc(lospace, npages, kind);
if (!ret) {
perror("weird: we have the space but mmap didn't work");
GC_CRASH();
}
return ret;
}
static void
collect_for_small_allocation(void *mut) {
trigger_collection(mut, GC_COLLECTION_ANY);
}
void*
gc_allocate_slow(struct gc_mutator *mut, size_t size,
enum gc_allocation_kind kind) {
GC_ASSERT(size > 0); // allocating 0 bytes would be silly
if (size > gc_allocator_large_threshold())
return allocate_large(mut, size, compute_trace_kind(kind));
struct gc_heap *heap = mutator_heap(mut);
while (1) {
struct gc_ref ret = nofl_allocate(&mut->allocator, heap_nofl_space(heap),
size, kind);
if (!gc_ref_is_null(ret))
return gc_ref_heap_object(ret);
if (trigger_collection(mut, GC_COLLECTION_ANY))
continue;
return heap->allocation_failure(heap, size);
}
}
void
gc_pin_object(struct gc_mutator *mut, struct gc_ref ref) {
struct nofl_space *nofl = heap_nofl_space(mutator_heap(mut));
if (nofl_space_contains(nofl, ref))
nofl_space_pin_object(nofl, ref);
// Otherwise if it's a large or external object, it won't move.
}
int
gc_object_is_old_generation_slow(struct gc_mutator *mut, struct gc_ref obj) {
if (!GC_GENERATIONAL)
return 0;
struct gc_heap *heap = mutator_heap(mut);
struct nofl_space *nofl_space = heap_nofl_space(heap);
if (nofl_space_contains(nofl_space, obj))
return nofl_space_is_survivor(nofl_space, obj);
struct large_object_space *lospace = heap_large_object_space(heap);
if (large_object_space_contains(lospace, obj))
return large_object_space_is_survivor(lospace, obj);
return 0;
}
void
gc_write_barrier_slow(struct gc_mutator *mut, struct gc_ref obj,
size_t obj_size, struct gc_edge edge,
struct gc_ref new_val) {
GC_ASSERT(!gc_ref_is_null(new_val));
if (!GC_GENERATIONAL) return;
if (gc_object_is_old_generation_slow(mut, new_val))
return;
struct gc_heap *heap = mutator_heap(mut);
if ((obj_size <= gc_allocator_large_threshold())
? nofl_space_remember_edge(heap_nofl_space(heap), obj, edge)
: large_object_space_remember_edge(heap_large_object_space(heap),
obj, edge))
gc_field_set_writer_add_edge(&mut->logger, edge);
}
struct gc_ephemeron*
gc_allocate_ephemeron(struct gc_mutator *mut) {
struct gc_ref ret =
gc_ref_from_heap_object(gc_allocate(mut, gc_ephemeron_size(),
GC_ALLOCATION_TAGGED));
nofl_space_set_ephemeron_flag(ret);
return gc_ref_heap_object(ret);
}
void
gc_ephemeron_init(struct gc_mutator *mut, struct gc_ephemeron *ephemeron,
struct gc_ref key, struct gc_ref value) {
gc_ephemeron_init_internal(mutator_heap(mut), ephemeron, key, value);
// No write barrier: we require that the ephemeron be newer than the
// key or the value.
}
struct gc_pending_ephemerons *
gc_heap_pending_ephemerons(struct gc_heap *heap) {
return heap->pending_ephemerons;
}
unsigned
gc_heap_ephemeron_trace_epoch(struct gc_heap *heap) {
return heap->count;
}
struct gc_finalizer*
gc_allocate_finalizer(struct gc_mutator *mut) {
return gc_allocate(mut, gc_finalizer_size(), GC_ALLOCATION_TAGGED);
}
void
gc_finalizer_attach(struct gc_mutator *mut, struct gc_finalizer *finalizer,
unsigned priority, struct gc_ref object,
struct gc_ref closure) {
gc_finalizer_init_internal(finalizer, object, closure);
gc_finalizer_attach_internal(mutator_heap(mut)->finalizer_state,
finalizer, priority);
// No write barrier.
}
struct gc_finalizer*
gc_pop_finalizable(struct gc_mutator *mut) {
return gc_finalizer_state_pop(mutator_heap(mut)->finalizer_state);
}
void
gc_set_finalizer_callback(struct gc_heap *heap,
gc_finalizer_callback callback) {
gc_finalizer_state_set_callback(heap->finalizer_state, callback);
}
static int
heap_prepare_pending_ephemerons(struct gc_heap *heap) {
struct gc_pending_ephemerons *cur = heap->pending_ephemerons;
size_t target = heap->size * heap->pending_ephemerons_size_factor;
double slop = heap->pending_ephemerons_size_slop;
heap->pending_ephemerons = gc_prepare_pending_ephemerons(cur, target, slop);
return !!heap->pending_ephemerons;
}
struct gc_options {
struct gc_common_options common;
};
int
gc_option_from_string(const char *str) {
return gc_common_option_from_string(str);
}
struct gc_options*
gc_allocate_options(void) {
struct gc_options *ret = malloc(sizeof(struct gc_options));
gc_init_common_options(&ret->common);
return ret;
}
int
gc_options_set_int(struct gc_options *options, int option, int value) {
return gc_common_options_set_int(&options->common, option, value);
}
int
gc_options_set_size(struct gc_options *options, int option,
size_t value) {
return gc_common_options_set_size(&options->common, option, value);
}
int
gc_options_set_double(struct gc_options *options, int option,
double value) {
return gc_common_options_set_double(&options->common, option, value);
}
int
gc_options_parse_and_set(struct gc_options *options, int option,
const char *value) {
return gc_common_options_parse_and_set(&options->common, option, value);
}
// with heap lock
static uint64_t allocation_counter(struct gc_heap *heap) {
uint64_t ret = heap->total_allocated_bytes_at_last_gc;
nofl_space_add_to_allocation_counter(heap_nofl_space(heap), &ret);
large_object_space_add_to_allocation_counter(heap_large_object_space(heap),
&ret);
return ret;
}
uint64_t gc_allocation_counter(struct gc_heap *heap) {
pthread_mutex_lock(&heap->lock);
uint64_t ret = allocation_counter(heap);
pthread_mutex_unlock(&heap->lock);
return ret;
}
static uint64_t allocation_counter_from_thread(struct gc_heap *heap) {
if (pthread_mutex_trylock(&heap->lock)) return 0;
uint64_t ret = allocation_counter(heap);
pthread_mutex_unlock(&heap->lock);
return ret;
}
static void set_heap_size_from_thread(struct gc_heap *heap, size_t size) {
if (pthread_mutex_trylock(&heap->lock)) return;
resize_heap(heap, size);
pthread_mutex_unlock(&heap->lock);
}
static void* allocation_failure(struct gc_heap *heap, size_t size) {
fprintf(stderr, "ran out of space, heap size %zu\n", heap->size);
GC_CRASH();
return NULL;
}
void gc_heap_set_allocation_failure_handler(struct gc_heap *heap,
void* (*handler)(struct gc_heap*,
size_t)) {
heap->allocation_failure = handler;
}
static int
heap_init(struct gc_heap *heap, const struct gc_options *options) {
// *heap is already initialized to 0.
gc_field_set_init(&heap->remembered_set);
pthread_mutex_init(&heap->lock, NULL);
pthread_cond_init(&heap->mutator_cond, NULL);
pthread_cond_init(&heap->collector_cond, NULL);
heap->size = heap->size_at_last_gc = options->common.heap_size;
if (!gc_tracer_init(&heap->tracer, heap, options->common.parallelism))
GC_CRASH();
heap->pending_ephemerons_size_factor = 0.005;
heap->pending_ephemerons_size_slop = 0.5;
heap->fragmentation_low_threshold = 0.05;
heap->fragmentation_high_threshold = 0.10;
heap->minor_gc_yield_threshold = 0.30;
heap->minimum_major_gc_yield_threshold = 0.05;
heap->major_gc_yield_threshold =
clamp_major_gc_yield_threshold(heap, heap->minor_gc_yield_threshold);
if (!heap_prepare_pending_ephemerons(heap))
GC_CRASH();
heap->finalizer_state = gc_make_finalizer_state();
if (!heap->finalizer_state)
GC_CRASH();
heap->background_thread = gc_make_background_thread();
heap->sizer = gc_make_heap_sizer(heap, &options->common,
allocation_counter_from_thread,
set_heap_size_from_thread,
heap->background_thread);
heap->allocation_failure = allocation_failure;
return 1;
}
int
gc_init(const struct gc_options *options, struct gc_stack_addr stack_base,
struct gc_heap **heap, struct gc_mutator **mut,
struct gc_event_listener event_listener,
void *event_listener_data) {
GC_ASSERT_EQ(gc_allocator_small_granule_size(), NOFL_GRANULE_SIZE);
GC_ASSERT_EQ(gc_allocator_large_threshold(), LARGE_OBJECT_THRESHOLD);
GC_ASSERT_EQ(gc_allocator_allocation_pointer_offset(),
offsetof(struct nofl_allocator, alloc));
GC_ASSERT_EQ(gc_allocator_allocation_limit_offset(),
offsetof(struct nofl_allocator, sweep));
GC_ASSERT_EQ(gc_allocator_alloc_table_alignment(), NOFL_SLAB_SIZE);
GC_ASSERT_EQ(gc_allocator_alloc_table_begin_pattern(GC_ALLOCATION_TAGGED),
NOFL_METADATA_BYTE_YOUNG | NOFL_METADATA_BYTE_TRACE_PRECISELY);
GC_ASSERT_EQ(gc_allocator_alloc_table_begin_pattern(GC_ALLOCATION_TAGGED_POINTERLESS),
NOFL_METADATA_BYTE_YOUNG | NOFL_METADATA_BYTE_TRACE_NONE);
if (GC_CONSERVATIVE_TRACE) {
GC_ASSERT_EQ(gc_allocator_alloc_table_begin_pattern(GC_ALLOCATION_UNTAGGED_CONSERVATIVE),
NOFL_METADATA_BYTE_YOUNG | NOFL_METADATA_BYTE_TRACE_CONSERVATIVELY);
GC_ASSERT_EQ(gc_allocator_alloc_table_begin_pattern(GC_ALLOCATION_UNTAGGED_POINTERLESS),
NOFL_METADATA_BYTE_YOUNG | NOFL_METADATA_BYTE_TRACE_NONE);
} else {
GC_ASSERT_EQ(gc_allocator_alloc_table_begin_pattern(GC_ALLOCATION_UNTAGGED_POINTERLESS),
NOFL_METADATA_BYTE_YOUNG | NOFL_METADATA_BYTE_TRACE_NONE |
NOFL_METADATA_BYTE_PINNED);
}
GC_ASSERT_EQ(gc_allocator_alloc_table_end_pattern(), NOFL_METADATA_BYTE_END);
if (GC_GENERATIONAL) {
GC_ASSERT_EQ(gc_write_barrier_field_table_alignment(), NOFL_SLAB_SIZE);
GC_ASSERT_EQ(gc_write_barrier_field_fields_per_byte(),
NOFL_GRANULE_SIZE / sizeof(uintptr_t));
GC_ASSERT_EQ(gc_write_barrier_field_first_bit_pattern(),
NOFL_METADATA_BYTE_LOGGED_0);
}
*heap = calloc(1, sizeof(struct gc_heap));
if (!*heap) GC_CRASH();
if (!heap_init(*heap, options))
GC_CRASH();
(*heap)->event_listener = event_listener;
(*heap)->event_listener_data = event_listener_data;
HEAP_EVENT(*heap, init, (*heap)->size);
struct nofl_space *space = heap_nofl_space(*heap);
if (!nofl_space_init(space, (*heap)->size,
options->common.parallelism != 1,
(*heap)->fragmentation_low_threshold,
(*heap)->background_thread)) {
free(*heap);
*heap = NULL;
return 0;
}
if (!large_object_space_init(heap_large_object_space(*heap), *heap,
(*heap)->background_thread))
GC_CRASH();
*mut = calloc(1, sizeof(struct gc_mutator));
if (!*mut) GC_CRASH();
gc_stack_init(&(*mut)->stack, stack_base);
add_mutator(*heap, *mut);
gc_background_thread_start((*heap)->background_thread);
return 1;
}
struct gc_mutator*
gc_init_for_thread(struct gc_stack_addr stack_base, struct gc_heap *heap) {
struct gc_mutator *ret = calloc(1, sizeof(struct gc_mutator));
if (!ret)
GC_CRASH();
gc_stack_init(&ret->stack, stack_base);
add_mutator(heap, ret);
return ret;
}
void
gc_finish_for_thread(struct gc_mutator *mut) {
remove_mutator(mutator_heap(mut), mut);
free(mut);
}
static void
deactivate_mutator(struct gc_heap *heap, struct gc_mutator *mut) {
GC_ASSERT(mut->next == NULL);
nofl_allocator_finish(&mut->allocator, heap_nofl_space(heap));
if (GC_GENERATIONAL)
gc_field_set_writer_release_buffer(&mut->logger);
heap_lock(heap);
heap->inactive_mutator_count++;
gc_stack_capture_hot(&mut->stack);
if (all_mutators_stopped(heap))
pthread_cond_signal(&heap->collector_cond);
heap_unlock(heap);
}
static void
reactivate_mutator(struct gc_heap *heap, struct gc_mutator *mut) {
heap_lock(heap);
while (mutators_are_stopping(heap))
pthread_cond_wait(&heap->mutator_cond, &heap->lock);
heap->inactive_mutator_count--;
heap_unlock(heap);
}
void*
gc_call_without_gc(struct gc_mutator *mut, void* (*f)(void*), void *data) {
struct gc_heap *heap = mutator_heap(mut);
deactivate_mutator(heap, mut);
void *ret = f(data);
reactivate_mutator(heap, mut);
return ret;
}
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