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Refactor CommandQueueMT

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* RingBuffer had no reason to be in this context
* A single buffer is used that can grow as much as the game needs.

This should make thread loading entirely reliable.
This commit is contained in:
reduz 2021-06-09 12:09:31 -03:00
parent 0818a466c0
commit c66b2651a6
7 changed files with 39 additions and 211 deletions
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29
core/templates/command_queue_mt.cpp
View file

@ -70,35 +70,7 @@ CommandQueueMT::SyncSemaphore *CommandQueueMT::_alloc_sync_sem() {
return &sync_sems[idx];
}
bool CommandQueueMT::dealloc_one() {
tryagain:
if (dealloc_ptr == (write_ptr_and_epoch >> 1)) {
// The queue is empty
return false;
}
uint32_t size = *(uint32_t *)&command_mem[dealloc_ptr];
if (size == 0) {
// End of command buffer wrap down
dealloc_ptr = 0;
goto tryagain;
}
if (size & 1) {
// Still used, nothing can be deallocated
return false;
}
dealloc_ptr += (size >> 1) + 8;
return true;
}
CommandQueueMT::CommandQueueMT(bool p_sync) {
command_mem_size = GLOBAL_DEF_RST("memory/limits/command_queue/multithreading_queue_size_kb", DEFAULT_COMMAND_MEM_SIZE_KB);
ProjectSettings::get_singleton()->set_custom_property_info("memory/limits/command_queue/multithreading_queue_size_kb", PropertyInfo(Variant::INT, "memory/limits/command_queue/multithreading_queue_size_kb", PROPERTY_HINT_RANGE, "1,4096,1,or_greater"));
command_mem_size *= 1024;
command_mem = (uint8_t *)memalloc(command_mem_size);
if (p_sync) {
sync = memnew(Semaphore);
}
@ -108,5 +80,4 @@ CommandQueueMT::~CommandQueueMT() {
if (sync) {
memdelete(sync);
}
memfree(command_mem);
}

167
core/templates/command_queue_mt.h
View file

@ -34,6 +34,8 @@
#include "core/os/memory.h"
#include "core/os/mutex.h"
#include "core/os/semaphore.h"
#include "core/string/print_string.h"
#include "core/templates/local_vector.h"
#include "core/templates/simple_type.h"
#include "core/typedefs.h"
@ -334,11 +336,7 @@ class CommandQueueMT {
SYNC_SEMAPHORES = 8
};
uint8_t *command_mem = nullptr;
uint32_t read_ptr_and_epoch = 0;
uint32_t write_ptr_and_epoch = 0;
uint32_t dealloc_ptr = 0;
uint32_t command_mem_size = 0;
LocalVector<uint8_t> command_mem;
SyncSemaphore sync_sems[SYNC_SEMAPHORES];
Mutex mutex;
Semaphore *sync = nullptr;
@ -346,138 +344,47 @@ class CommandQueueMT {
template <class T>
T *allocate() {
// alloc size is size+T+safeguard
uint32_t alloc_size = ((sizeof(T) + 8 - 1) & ~(8 - 1)) + 8;
// Assert that the buffer is big enough to hold at least two messages.
ERR_FAIL_COND_V(alloc_size * 2 + sizeof(uint32_t) > command_mem_size, nullptr);
tryagain:
uint32_t write_ptr = write_ptr_and_epoch >> 1;
if (write_ptr < dealloc_ptr) {
// behind dealloc_ptr, check that there is room
if ((dealloc_ptr - write_ptr) <= alloc_size) {
// There is no more room, try to deallocate something
if (dealloc_one()) {
goto tryagain;
}
return nullptr;
}
} else {
// ahead of dealloc_ptr, check that there is room
if ((command_mem_size - write_ptr) < alloc_size + sizeof(uint32_t)) {
// no room at the end, wrap down;
if (dealloc_ptr == 0) { // don't want write_ptr to become dealloc_ptr
// There is no more room, try to deallocate something
if (dealloc_one()) {
goto tryagain;
}
return nullptr;
}
// if this happens, it's a bug
ERR_FAIL_COND_V((command_mem_size - write_ptr) < 8, nullptr);
// zero means, wrap to beginning
uint32_t *p = (uint32_t *)&command_mem[write_ptr];
*p = 1;
write_ptr_and_epoch = 0 | (1 & ~write_ptr_and_epoch); // Invert epoch.
// See if we can get the thread to run and clear up some more space while we wait.
// This is required if alloc_size * 2 + 4 > COMMAND_MEM_SIZE
if (sync) {
sync->post();
}
goto tryagain;
}
}
// Allocate the size and the 'in use' bit.
// First bit used to mark if command is still in use (1)
// or if it has been destroyed and can be deallocated (0).
uint32_t size = (sizeof(T) + 8 - 1) & ~(8 - 1);
uint32_t *p = (uint32_t *)&command_mem[write_ptr];
*p = (size << 1) | 1;
write_ptr += 8;
// allocate the command
T *cmd = memnew_placement(&command_mem[write_ptr], T);
write_ptr += size;
write_ptr_and_epoch = (write_ptr << 1) | (write_ptr_and_epoch & 1);
uint32_t alloc_size = ((sizeof(T) + 8 - 1) & ~(8 - 1));
uint64_t size = command_mem.size();
command_mem.resize(size + alloc_size + 8);
*(uint64_t *)&command_mem[size] = alloc_size;
T *cmd = memnew_placement(&command_mem[size + 8], T);
return cmd;
}
template <class T>
T *allocate_and_lock() {
lock();
T *ret;
while ((ret = allocate<T>()) == nullptr) {
unlock();
// sleep a little until fetch happened and some room is made
wait_for_flush();
lock();
}
T *ret = allocate<T>();
return ret;
}
bool flush_one(bool p_lock = true) {
if (p_lock) {
lock();
}
tryagain:
void _flush() {
lock();
// tried to read an empty queue
if (read_ptr_and_epoch == write_ptr_and_epoch) {
if (p_lock) {
unlock();
}
return false;
uint64_t read_ptr = 0;
uint64_t limit = command_mem.size();
while (read_ptr < limit) {
uint64_t size = *(uint64_t *)&command_mem[read_ptr];
read_ptr += 8;
CommandBase *cmd = reinterpret_cast<CommandBase *>(&command_mem[read_ptr]);
cmd->call(); //execute the function
cmd->post(); //release in case it needs sync/ret
cmd->~CommandBase(); //should be done, so erase the command
read_ptr += size;
}
uint32_t read_ptr = read_ptr_and_epoch >> 1;
uint32_t size_ptr = read_ptr;
uint32_t size = *(uint32_t *)&command_mem[read_ptr] >> 1;
if (size == 0) {
*(uint32_t *)&command_mem[read_ptr] = 0; // clear in-use bit.
//end of ringbuffer, wrap
read_ptr_and_epoch = 0 | (1 & ~read_ptr_and_epoch); // Invert epoch.
goto tryagain;
}
read_ptr += 8;
CommandBase *cmd = reinterpret_cast<CommandBase *>(&command_mem[read_ptr]);
read_ptr += size;
read_ptr_and_epoch = (read_ptr << 1) | (read_ptr_and_epoch & 1);
if (p_lock) {
unlock();
}
cmd->call();
if (p_lock) {
lock();
}
cmd->post();
cmd->~CommandBase();
*(uint32_t *)&command_mem[size_ptr] &= ~1;
if (p_lock) {
unlock();
}
return true;
command_mem.clear();
unlock();
}
void lock();
void unlock();
void wait_for_flush();
SyncSemaphore *_alloc_sync_sem();
bool dealloc_one();
public:
/* NORMAL PUSH COMMANDS */
@ -492,23 +399,19 @@ public:
DECL_PUSH_AND_SYNC(0)
SPACE_SEP_LIST(DECL_PUSH_AND_SYNC, 15)
void wait_and_flush_one() {
ERR_FAIL_COND(!sync);
sync->wait();
flush_one();
}
_FORCE_INLINE_ void flush_if_pending() {
if (unlikely(read_ptr_and_epoch != write_ptr_and_epoch)) {
flush_all();
if (unlikely(command_mem.size() > 0)) {
_flush();
}
}
void flush_all() {
//ERR_FAIL_COND(sync);
lock();
while (flush_one(false)) {
}
unlock();
_flush();
}
void wait_and_flush() {
ERR_FAIL_COND(!sync);
sync->wait();
_flush();
}
CommandQueueMT(bool p_sync);

2
doc/classes/ProjectSettings.xml
View file

@ -1139,8 +1139,6 @@
<member name="layer_names/3d_render/layer_9" type="String" setter="" getter="" default="&quot;&quot;">
Optional name for the 3D render layer 9. If left empty, the layer will display as "Layer 9".
</member>
<member name="memory/limits/command_queue/multithreading_queue_size_kb" type="int" setter="" getter="" default="256">
</member>
<member name="memory/limits/message_queue/max_size_kb" type="int" setter="" getter="" default="4096">
Godot uses a message queue to defer some function calls. If you run out of space on it (you will see an error), you can increase the size here.
</member>

2
servers/physics_2d/physics_server_2d_wrap_mt.cpp
View file

@ -56,7 +56,7 @@ void PhysicsServer2DWrapMT::thread_loop() {
step_thread_up.set();
while (!exit.is_set()) {
// flush commands one by one, until exit is requested
command_queue.wait_and_flush_one();
command_queue.wait_and_flush();
}
command_queue.flush_all(); // flush all

2
servers/physics_3d/physics_server_3d_wrap_mt.cpp
View file

@ -56,7 +56,7 @@ void PhysicsServer3DWrapMT::thread_loop() {
step_thread_up = true;
while (!exit) {
// flush commands one by one, until exit is requested
command_queue.wait_and_flush_one();
command_queue.wait_and_flush();
}
command_queue.flush_all(); // flush all

2
servers/rendering/rendering_server_default.cpp
View file

@ -358,7 +358,7 @@ void RenderingServerDefault::_thread_loop() {
draw_thread_up.set();
while (!exit.is_set()) {
// flush commands one by one, until exit is requested
command_queue.wait_and_flush_one();
command_queue.wait_and_flush();
}
command_queue.flush_all(); // flush all

46
tests/test_command_queue.h
View file

@ -156,7 +156,7 @@ public:
command_queue.flush_all();
}
for (int i = 0; i < message_count_to_read; i++) {
command_queue.wait_and_flush_one();
command_queue.wait_and_flush();
}
message_count_to_read = 0;
@ -276,50 +276,6 @@ TEST_CASE("[CommandQueue] Test Queue Basics") {
ProjectSettings::get_singleton()->property_get_revert(COMMAND_QUEUE_SETTING));
}
TEST_CASE("[CommandQueue] Test Waiting at Queue Full") {
const char *COMMAND_QUEUE_SETTING = "memory/limits/command_queue/multithreading_queue_size_kb";
ProjectSettings::get_singleton()->set_setting(COMMAND_QUEUE_SETTING, 1);
SharedThreadState sts;
sts.init_threads();
int msgs_to_add = 24; // a queue of size 1kB fundamentally cannot fit 24 matrices.
for (int i = 0; i < msgs_to_add; i++) {
sts.add_msg_to_write(SharedThreadState::TEST_MSG_FUNC1_TRANSFORM);
}
sts.writer_threadwork.main_start_work();
// If we call main_wait_for_done, we will deadlock. So instead...
sts.message_count_to_read = 1;
sts.reader_threadwork.main_start_work();
sts.reader_threadwork.main_wait_for_done();
CHECK_MESSAGE(sts.func1_count == 1,
"Reader should have read one message");
CHECK_MESSAGE(sts.during_writing,
"Writer thread should still be blocked on writing.");
sts.message_count_to_read = msgs_to_add - 3;
sts.reader_threadwork.main_start_work();
sts.reader_threadwork.main_wait_for_done();
CHECK_MESSAGE(sts.func1_count >= msgs_to_add - 3,
"Reader should have read most messages");
sts.writer_threadwork.main_wait_for_done();
CHECK_MESSAGE(sts.during_writing == false,
"Writer thread should no longer be blocked on writing.");
sts.message_count_to_read = 2;
sts.reader_threadwork.main_start_work();
sts.reader_threadwork.main_wait_for_done();
sts.message_count_to_read = -1;
sts.reader_threadwork.main_start_work();
sts.reader_threadwork.main_wait_for_done();
CHECK_MESSAGE(sts.func1_count == msgs_to_add,
"Reader should have read all messages");
sts.destroy_threads();
CHECK_MESSAGE(sts.func1_count == msgs_to_add,
"Reader should have read no additional messages after join");
ProjectSettings::get_singleton()->set_setting(COMMAND_QUEUE_SETTING,
ProjectSettings::get_singleton()->property_get_revert(COMMAND_QUEUE_SETTING));
}
TEST_CASE("[CommandQueue] Test Queue Wrapping to same spot.") {
const char *COMMAND_QUEUE_SETTING = "memory/limits/command_queue/multithreading_queue_size_kb";
ProjectSettings::get_singleton()->set_setting(COMMAND_QUEUE_SETTING, 1);