/* Allocate the specified amount of memory from the nursery. Will
* trigger a GC run if there is not enough. */
void * MVM_gc_allocate_nursery(MVMThreadContext *tc, size_t size) {
void *allocated;
/* Before an allocation is a GC safe-point and thus a good GC sync point
* also; check if we've been signalled to collect. */
/* Don't use a MVM_load(&tc->gc_status) here for performance, it's okay
* if the interrupt is delayed a bit. */
if (tc->gc_status)
MVM_gc_enter_from_interrupt(tc);
/* Guard against 0-byte allocation. */
if (size > 0) {
/* Do a GC run if this allocation won't fit in what we have
* left in the nursery. Note this is a loop to handle a
* pathological case: all the objects in the nursery are very
* young and thus survive in the nursery, meaning that no space
* actually gets freed up. The next run will promote them to the
* second generation. Note that this circumstance is exceptionally
* unlikely in any non-contrived situation. */
while ((char *)tc->nursery_alloc + size >= (char *)tc->nursery_alloc_limit) {
if (size > MVM_NURSERY_SIZE)
MVM_panic(MVM_exitcode_gcalloc, "Attempt to allocate more than the maximum nursery size");
MVM_gc_enter_from_allocator(tc);
}
/* Allocate (just bump the pointer). */
allocated = tc->nursery_alloc;
tc->nursery_alloc = (char *)tc->nursery_alloc + size;
}
else {
MVM_panic(MVM_exitcode_gcalloc, "Cannot allocate 0 bytes of memory in the nursery");
}
return allocated;
}
/* Called by a thread to indicate it is about to enter a blocking operation.
* This tells any thread that is coordinating a GC run that this thread will
* be unable to participate. */
void MVM_gc_mark_thread_blocked(MVMThreadContext *tc) {
/* This may need more than one attempt. */
while (1) {
/* Try to set it from running to unable - the common case. */
if (MVM_cas(&tc->gc_status, MVMGCStatus_NONE,
MVMGCStatus_UNABLE) == MVMGCStatus_NONE)
return;
/* The only way this can fail is if another thread just decided we're to
* participate in a GC run. */
if (MVM_load(&tc->gc_status) == MVMGCStatus_INTERRUPT)
MVM_gc_enter_from_interrupt(tc);
else
MVM_panic(MVM_exitcode_gcorch, "Invalid GC status observed; aborting");
}
}
/* This is called when the allocator finds it has run out of memory and wants
* to trigger a GC run. In this case, it's possible (probable, really) that it
* will need to do that triggering, notifying other running threads that the
* time has come to GC. */
void MVM_gc_enter_from_allocator(MVMThreadContext *tc) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Entered from allocate\n");
/* Try to start the GC run. */
if (MVM_trycas(&tc->instance->gc_start, 0, 1)) {
MVMThread *last_starter = NULL;
MVMuint32 num_threads = 0;
MVMuint32 is_full;
/* Need to wait for other threads to reset their gc_status. */
while (MVM_load(&tc->instance->gc_ack)) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : waiting for other thread's gc_ack\n");
MVM_platform_thread_yield();
}
/* We are the winner of the GC starting race. This gives us some
* extra responsibilities as well as doing the usual things.
* First, increment GC sequence number. */
MVM_incr(&tc->instance->gc_seq_number);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE,
"Thread %d run %d : GC thread elected coordinator: starting gc seq %d\n",
(int)MVM_load(&tc->instance->gc_seq_number));
/* Decide if it will be a full collection. */
is_full = is_full_collection(tc);
/* If profiling, record that GC is starting. */
if (tc->instance->profiling)
MVM_profiler_log_gc_start(tc, is_full);
/* Ensure our stolen list is empty. */
tc->gc_work_count = 0;
/* Flag that we didn't agree on this run that all the in-trays are
* cleared (a responsibility of the co-ordinator. */
MVM_store(&tc->instance->gc_intrays_clearing, 1);
/* We'll take care of our own work. */
add_work(tc, tc);
/* Find other threads, and signal or steal. */
do {
MVMThread *threads = (MVMThread *)MVM_load(&tc->instance->threads);
if (threads && threads != last_starter) {
MVMThread *head = threads;
MVMuint32 add;
while ((threads = (MVMThread *)MVM_casptr(&tc->instance->threads, head, NULL)) != head) {
head = threads;
}
add = signal_all_but(tc, head, last_starter);
last_starter = head;
if (add) {
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Found %d other threads\n", add);
MVM_add(&tc->instance->gc_start, add);
num_threads += add;
}
}
/* If there's an event loop thread, wake it up to participate. */
if (tc->instance->event_loop_wakeup)
uv_async_send(tc->instance->event_loop_wakeup);
} while (MVM_load(&tc->instance->gc_start) > 1);
/* Sanity checks. */
if (!MVM_trycas(&tc->instance->threads, NULL, last_starter))
MVM_panic(MVM_exitcode_gcorch, "threads list corrupted\n");
if (MVM_load(&tc->instance->gc_finish) != 0)
MVM_panic(MVM_exitcode_gcorch, "Finish votes was %"MVM_PRSz"\n", MVM_load(&tc->instance->gc_finish));
/* gc_ack gets an extra so the final acknowledger
* can also free the STables. */
MVM_store(&tc->instance->gc_finish, num_threads + 1);
MVM_store(&tc->instance->gc_ack, num_threads + 2);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : finish votes is %d\n",
(int)MVM_load(&tc->instance->gc_finish));
/* Now we're ready to start, zero promoted since last full collection
* counter if this is a full collect. */
if (is_full)
MVM_store(&tc->instance->gc_promoted_bytes_since_last_full, 0);
/* Signal to the rest to start */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : coordinator signalling start\n");
if (MVM_decr(&tc->instance->gc_start) != 1)
MVM_panic(MVM_exitcode_gcorch, "Start votes was %"MVM_PRSz"\n", MVM_load(&tc->instance->gc_start));
/* Start collecting. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : coordinator entering run_gc\n");
run_gc(tc, MVMGCWhatToDo_All);
/* Free any STables that have been marked for deletion. It's okay for
* us to muck around in another thread's fromspace while it's mutating
* tospace, really. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Freeing STables if needed\n");
MVM_gc_collect_free_stables(tc);
/* If profiling, record that GC is over. */
if (tc->instance->profiling)
MVM_profiler_log_gc_end(tc);
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : GC complete (cooridnator)\n");
}
else {
/* Another thread beat us to starting the GC sync process. Thus, act as
* if we were interrupted to GC. */
GCDEBUG_LOG(tc, MVM_GC_DEBUG_ORCHESTRATE, "Thread %d run %d : Lost coordinator election\n");
MVM_gc_enter_from_interrupt(tc);
}
}
/* This is called when the allocator finds it has run out of memory and wants
* to trigger a GC run. In this case, it's possible (probable, really) that it
* will need to do that triggering, notifying other running threads that the
* time has come to GC. */
void MVM_gc_enter_from_allocator(MVMThreadContext *tc) {
GCORCH_LOG(tc, "Thread %d run %d : Entered from allocate\n");
/* Try to start the GC run. */
if (MVM_trycas(&tc->instance->gc_start, 0, 1)) {
MVMThread *last_starter = NULL;
MVMuint32 num_threads = 0;
/* We are the winner of the GC starting race. This gives us some
* extra responsibilities as well as doing the usual things.
* First, increment GC sequence number. */
tc->instance->gc_seq_number++;
GCORCH_LOG(tc, "Thread %d run %d : GC thread elected coordinator: starting gc seq %d\n", tc->instance->gc_seq_number);
/* Ensure our stolen list is empty. */
tc->gc_work_count = 0;
/* need to wait for other threads to reset their gc_status. */
while (tc->instance->gc_ack)
apr_thread_yield();
add_work(tc, tc);
/* grab our child */
signal_child(tc);
do {
if (tc->instance->threads && tc->instance->threads != last_starter) {
MVMThread *head;
MVMuint32 add;
while (!MVM_trycas(&tc->instance->threads, (head = tc->instance->threads), NULL));
add = signal_all_but(tc, head, last_starter);
last_starter = head;
if (add) {
GCORCH_LOG(tc, "Thread %d run %d : Found %d other threads\n", add);
MVM_atomic_add(&tc->instance->gc_start, add);
num_threads += add;
}
}
} while (tc->instance->gc_start > 1);
if (!MVM_trycas(&tc->instance->threads, NULL, last_starter))
MVM_panic(MVM_exitcode_gcorch, "threads list corrupted\n");
if (tc->instance->gc_finish != 0)
MVM_panic(MVM_exitcode_gcorch, "finish votes was %d\n", tc->instance->gc_finish);
tc->instance->gc_ack = tc->instance->gc_finish = num_threads + 1;
GCORCH_LOG(tc, "Thread %d run %d : finish votes is %d\n", (int)tc->instance->gc_finish);
/* signal to the rest to start */
if (MVM_atomic_decr(&tc->instance->gc_start) != 1)
MVM_panic(MVM_exitcode_gcorch, "start votes was %d\n", tc->instance->gc_finish);
run_gc(tc, MVMGCWhatToDo_All);
}
else {
/* Another thread beat us to starting the GC sync process. Thus, act as
* if we were interrupted to GC. */
GCORCH_LOG(tc, "Thread %d run %d : Lost coordinator election\n");
MVM_gc_enter_from_interrupt(tc);
}
}
