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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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167
core/templates/command_queue_mt.h
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@ -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);