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Delay marking of finished tasks #48037

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Delay marking of finished tasks #48037

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80 changes: 74 additions & 6 deletions src/gc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2938,25 +2938,80 @@ static void jl_gc_queue_thread_local(jl_gc_mark_cache_t *gc_cache, jl_gc_mark_sp
}
task = jl_atomic_load_relaxed(&ptls2->current_task);
if (task) {
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "current task");
if (jl_atomic_load_relaxed(&task->_state)== JL_TASK_STATE_RUNNABLE) {
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "current task");
}
}
task = ptls2->next_task;
if (task) {
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "next task");
if (jl_atomic_load_relaxed(&task->_state)== JL_TASK_STATE_RUNNABLE) {
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "next task");
}
}
task = ptls2->previous_task;
if (task) { // shouldn't be necessary, but no reason not to
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "previous task");
if (jl_atomic_load_relaxed(&task->_state)== JL_TASK_STATE_RUNNABLE) {
gc_mark_queue_obj(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "previous task");
}
}
if (ptls2->previous_exception) {
gc_mark_queue_obj(gc_cache, sp, ptls2->previous_exception);
gc_heap_snapshot_record_root((jl_value_t*)ptls2->previous_exception, "previous exception");
}
}

// Treat fields of task as weakrefs, mark the task itself and discard
// some of it's fields.
STATIC_INLINE int gc_queue_task_weakly(jl_gc_mark_cache_t *gc_cache, jl_gc_mark_sp_t *sp, jl_task_t *task) JL_NOTSAFEPOINT
{
jl_value_t *obj = (jl_value_t*)jl_assume(task);
uintptr_t nptr = 0;
uintptr_t tag = 0;
uint8_t bits = 0;
if (!gc_try_setmark(obj, &nptr, &tag, &bits))
return (int)nptr;

task->result = jl_nothing;
task->start = jl_nothing;
task->tls = jl_nothing;
// TODO: Are there other fields we need to want to zero?
gc_mark_marked_obj_t data = {obj, tag, bits};
gc_mark_stack_push(gc_cache, sp, gc_mark_label_addrs[GC_MARK_L_marked_obj],
&data, sizeof(data), 1);
return (int)nptr;
}

static void jl_gc_queue_delayed_thread_local(jl_gc_mark_cache_t *gc_cache, jl_gc_mark_sp_t *sp,
jl_ptls_t ptls2)
{
jl_task_t *task;
task = jl_atomic_load_relaxed(&ptls2->current_task);
if (task) {
if (jl_atomic_load_relaxed(&task->_state)!= JL_TASK_STATE_RUNNABLE) {
gc_queue_task_weakly(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "current task (weak)");
}
}
task = ptls2->next_task;
if (task) {
if (jl_atomic_load_relaxed(&task->_state)!= JL_TASK_STATE_RUNNABLE) {
gc_queue_task_weakly(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "next task (weak)");

}
}
task = ptls2->previous_task;
if (task) { // shouldn't be necessary, but no reason not to
if (jl_atomic_load_relaxed(&task->_state)!= JL_TASK_STATE_RUNNABLE) {
gc_queue_task_weakly(gc_cache, sp, task);
gc_heap_snapshot_record_root((jl_value_t*)task, "previous task (weak)");
}
}
}

extern jl_value_t *cmpswap_names JL_GLOBALLY_ROOTED;
extern jl_task_t *wait_empty JL_GLOBALLY_ROOTED;

Expand Down Expand Up @@ -3222,6 +3277,19 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)
import_gc_state(ptls, &sp);
}
gc_mark_loop(ptls, sp);

// Tasks hold on to state quite a bit even after they are finished
// So we process the thread_local state of finished tasks delayed.
assert(gc_n_threads);
gc_mark_sp_init(gc_cache, &sp);
for (int t_i = 0; t_i < gc_n_threads; t_i++) {
jl_ptls_t ptls2 = gc_all_tls_states[t_i];
if (ptls2 == NULL)
continue;
jl_gc_queue_delayed_thread_local(gc_cache, &sp, ptls2);
}
gc_mark_loop(ptls, sp);

gc_mark_sp_init(gc_cache, &sp);
gc_num.since_sweep += gc_num.allocd;
JL_PROBE_GC_MARK_END(scanned_bytes, perm_scanned_bytes);
Expand Down