Finalize as many completed jobs as possible

Instead of finishing one job per thread per frame, now copy job pointers to an on-thread array and run their finalizers in one pass.

This means we can queue potentially 1000s of jobs in a single frame / load step without then needing to finalize them over the next 250 frames.

Potentially investigate an upper limit on the number of finalized jobs; e.g. 100/thread/frame to avoid frame hitches.

src/JobQueue.cpp

@@ -206,31 +206,36 @@ void AsyncJobQueue::Finish(Job *job, const uint8_t threadIdx)
 Uint32 AsyncJobQueue::FinishJobs()
 {
  PROFILE_SCOPED()
- Uint32 finished = 0;
+
+ // semi-magic number to avoid frivolous reallocs
+ m_finishedScratch.reserve(32);
 
  const uint32_t numRunners = m_runners.size();
  for (uint32_t i = 0; i < numRunners; ++i) {
  SDL_LockMutex(m_finishedLock[i]);
- if (m_finished[i].empty()) {
- SDL_UnlockMutex(m_finishedLock[i]);
- continue;
+
+ while (!m_finished[i].empty()) {
+ assert(m_finished[i].front());
+ m_finishedScratch.push_back(std::move(m_finished[i].front()));
+ m_finished[i].pop_front();
  }
- Job *job = m_finished[i].front();
- m_finished[i].pop_front();
- SDL_UnlockMutex(m_finishedLock[i]);
 
- assert(job);
+ SDL_UnlockMutex(m_finishedLock[i]);
+ }
 
+ for (Job *job : m_finishedScratch) {
  // if its already been cancelled then its taken care of, so we just forget about it
  if (!job->cancelled) {
  job->UnlinkHandle();
  job->OnFinish();
- finished++;
  }
 
  delete job;
  }
 
+ Uint32 finished = m_finishedScratch.size();
+ m_finishedScratch.clear();
+
  return finished;
 }
 
@@ -441,6 +446,7 @@ void SyncJobQueue::Cancel(Job *job)
 
 Uint32 SyncJobQueue::RunJobs(Uint32 count)
 {
+ PROFILE_SCOPED()
  Uint32 executed = 0;
  assert(count >= 1);
  for (Uint32 i = 0; i < count; ++i) {

src/JobQueue.h

@@ -198,6 +198,8 @@ class AsyncJobQueue : public JobQueue {
  SDL_mutex *m_finishedLock[MAX_THREADS];
 
  std::vector<JobRunner *> m_runners;
+ // scratch space for finishing jobs on main thread
+ std::vector<Job *> m_finishedScratch;
 
  bool m_shutdown;
 };