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Add parallel root-tracing phase

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This commit is contained in:
Andy Wingo 2024-07-10 15:46:11 +02:00
parent ff1e1b1d44
commit 5084730471
10 changed files with 231 additions and 34 deletions
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51
src/parallel-tracer.h
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@ -10,10 +10,17 @@
#include "debug.h"
#include "gc-inline.h"
#include "local-worklist.h"
#include "root-worklist.h"
#include "shared-worklist.h"
#include "spin.h"
#include "tracer.h"
#ifdef VERBOSE_LOGGING
#define LOG(...) fprintf (stderr, "LOG: " __VA_ARGS__)
#else
#define LOG(...) do { } while (0)
#endif
enum trace_worker_state {
TRACE_WORKER_STOPPED,
TRACE_WORKER_IDLE,
@ -36,6 +43,11 @@ struct gc_trace_worker {
struct gc_trace_worker_data *data;
};
static inline struct gc_trace_worker_data*
gc_trace_worker_data(struct gc_trace_worker *worker) {
return worker->data;
}
#define TRACE_WORKERS_MAX_COUNT 8
struct gc_tracer {
@ -45,6 +57,7 @@ struct gc_tracer {
long epoch;
pthread_mutex_t lock;
pthread_cond_t cond;
struct root_worklist roots;
struct gc_trace_worker workers[TRACE_WORKERS_MAX_COUNT];
};
@ -101,6 +114,7 @@ gc_tracer_init(struct gc_tracer *tracer, struct gc_heap *heap,
tracer->epoch = 0;
pthread_mutex_init(&tracer->lock, NULL);
pthread_cond_init(&tracer->cond, NULL);
root_worklist_init(&tracer->roots);
size_t desired_worker_count = parallelism;
ASSERT(desired_worker_count);
if (desired_worker_count > TRACE_WORKERS_MAX_COUNT)
@ -121,13 +135,18 @@ gc_tracer_init(struct gc_tracer *tracer, struct gc_heap *heap,
static void gc_tracer_prepare(struct gc_tracer *tracer) {
for (size_t i = 0; i < tracer->worker_count; i++)
tracer->workers[i].steal_id = 0;
tracer->workers[i].steal_id = (i + 1) % tracer->worker_count;
}
static void gc_tracer_release(struct gc_tracer *tracer) {
for (size_t i = 0; i < tracer->worker_count; i++)
shared_worklist_release(&tracer->workers[i].shared);
}
static inline void
gc_tracer_add_root(struct gc_tracer *tracer, struct gc_root root) {
root_worklist_push(&tracer->roots, root);
}
static inline void
tracer_unpark_all_workers(struct gc_tracer *tracer) {
long old_epoch =
@ -161,6 +180,7 @@ tracer_share(struct gc_trace_worker *worker) {
static inline void
gc_trace_worker_enqueue(struct gc_trace_worker *worker, struct gc_ref ref) {
ASSERT(gc_ref_is_heap_object(ref));
if (local_worklist_full(&worker->local))
tracer_share(worker);
local_worklist_push(&worker->local, ref);
@ -182,33 +202,33 @@ static struct gc_ref
trace_worker_steal_from_any(struct gc_trace_worker *worker,
struct gc_tracer *tracer) {
for (size_t i = 0; i < tracer->worker_count; i++) {
DEBUG("tracer #%zu: stealing from #%zu\n", worker->id, worker->steal_id);
LOG("tracer #%zu: stealing from #%zu\n", worker->id, worker->steal_id);
struct gc_ref obj = tracer_steal_from_worker(tracer, worker->steal_id);
if (gc_ref_is_heap_object(obj)) {
DEBUG("tracer #%zu: stealing got %p\n", worker->id,
LOG("tracer #%zu: stealing got %p\n", worker->id,
gc_ref_heap_object(obj));
return obj;
}
worker->steal_id = (worker->steal_id + 1) % tracer->worker_count;
}
DEBUG("tracer #%zu: failed to steal\n", worker->id);
LOG("tracer #%zu: failed to steal\n", worker->id);
return gc_ref_null();
}
static int
trace_worker_can_steal_from_any(struct gc_trace_worker *worker,
struct gc_tracer *tracer) {
DEBUG("tracer #%zu: checking if any worker has tasks\n", worker->id);
LOG("tracer #%zu: checking if any worker has tasks\n", worker->id);
for (size_t i = 0; i < tracer->worker_count; i++) {
int res = tracer_can_steal_from_worker(tracer, worker->steal_id);
if (res) {
DEBUG("tracer #%zu: worker #%zu has tasks!\n", worker->id,
LOG("tracer #%zu: worker #%zu has tasks!\n", worker->id,
worker->steal_id);
return 1;
}
worker->steal_id = (worker->steal_id + 1) % tracer->worker_count;
}
DEBUG("tracer #%zu: nothing to steal\n", worker->id);
LOG("tracer #%zu: nothing to steal\n", worker->id);
return 0;
}
@ -241,7 +261,7 @@ trace_worker_should_continue(struct gc_trace_worker *worker) {
return !done;
}
// spin
DEBUG("checking for termination: spinning #%zu\n", spin_count);
LOG("checking for termination: spinning #%zu\n", spin_count);
yield_for_spin(spin_count);
}
}
@ -254,13 +274,13 @@ trace_worker_steal(struct gc_trace_worker *worker) {
// overflowed. In that case avoid contention by trying to pop
// something from the worker's own queue.
{
DEBUG("tracer #%zu: trying to pop worker's own deque\n", worker->id);
LOG("tracer #%zu: trying to pop worker's own deque\n", worker->id);
struct gc_ref obj = shared_worklist_try_pop(&worker->shared);
if (gc_ref_is_heap_object(obj))
return obj;
}
DEBUG("tracer #%zu: trying to steal\n", worker->id);
LOG("tracer #%zu: trying to steal\n", worker->id);
struct gc_ref obj = trace_worker_steal_from_any(worker, tracer);
if (gc_ref_is_heap_object(obj))
return obj;
@ -279,6 +299,13 @@ trace_with_data(struct gc_tracer *tracer,
size_t n = 0;
DEBUG("tracer #%zu: running trace loop\n", worker->id);
do {
struct gc_root root = root_worklist_pop(&tracer->roots);
if (root.kind == GC_ROOT_KIND_NONE)
break;
trace_root(root, heap, worker);
} while (1);
do {
while (1) {
struct gc_ref ref;
@ -325,7 +352,8 @@ gc_tracer_trace(struct gc_tracer *tracer) {
ssize_t parallel_threshold =
LOCAL_WORKLIST_SIZE - LOCAL_WORKLIST_SHARE_AMOUNT;
if (shared_worklist_size(&tracer->workers[0].shared) >= parallel_threshold) {
if (root_worklist_size(&tracer->roots) > 1 ||
shared_worklist_size(&tracer->workers[0].shared) >= parallel_threshold) {
DEBUG("waking workers\n");
tracer_unpark_all_workers(tracer);
} else {
@ -333,6 +361,7 @@ gc_tracer_trace(struct gc_tracer *tracer) {
}
trace_worker_trace(&tracer->workers[0]);
root_worklist_reset(&tracer->roots);
DEBUG("trace finished\n");
}