Refactor CompilerThreadPool out of OpenGLDriver (#7067)

filament/backend/src/CompilerThreadPool.cpp

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "CompilerThreadPool.h"
+
+#include <memory>
+
+namespace filament::backend {
+
+using namespace utils;
+
+ProgramToken::~ProgramToken() = default;
+
+CompilerThreadPool::CompilerThreadPool() noexcept = default;
+
+CompilerThreadPool::~CompilerThreadPool() noexcept {
+    assert_invariant(mCompilerThreads.empty());
+    assert_invariant(mQueues[0].empty());
+    assert_invariant(mQueues[1].empty());
+}
+
+void CompilerThreadPool::init(uint32_t threadCount, JobSystem::Priority priority,
+        ThreadSetup&& threadSetup) noexcept {
+    auto setup = std::make_shared<ThreadSetup>(std::move(threadSetup));
+
+    for (size_t i = 0; i < threadCount; i++) {
+        mCompilerThreads.emplace_back([this, priority, setup]() {
+            // give the thread a name
+            JobSystem::setThreadName("CompilerThreadPool");
+            // run at a slightly lower priority than other filament threads
+            JobSystem::setThreadPriority(priority);
+
+            (*setup)();
+
+            // process jobs from the queue until we're asked to exit
+            while (!mExitRequested) {
+                std::unique_lock lock(mQueueLock);
+                mQueueCondition.wait(lock, [this]() {
+                    return  mExitRequested ||
+                            (!std::all_of( std::begin(mQueues), std::end(mQueues),
+                                    [](auto&& q) { return q.empty(); }));
+                });
+                if (!mExitRequested) {
+                    Job job;
+                    // use the first queue that's not empty
+                    auto& queue = [this]() -> auto& {
+                        for (auto& q: mQueues) {
+                            if (!q.empty()) {
+                                return q;
+                            }
+                        }
+                        return mQueues[0]; // we should never end-up here.
+                    }();
+                    assert_invariant(!queue.empty());
+                    std::swap(job, queue.front().second);
+                    queue.pop_front();
+
+                    // execute the job without holding any locks
+                    lock.unlock();
+                    job();
+                }
+            }
+        });
+
+    }
+}
+
+auto CompilerThreadPool::find(program_token_t const& token) -> std::pair<Queue&, Queue::iterator> {
+    for (auto&& q: mQueues) {
+        auto pos = std::find_if(q.begin(), q.end(), [&token](auto&& item) {
+            return item.first == token;
+        });
+        if (pos != q.end()) {
+            return { q, pos };
+        }
+    }
+    // this can happen if the program is being processed right now
+    return { mQueues[0], mQueues[0].end() };
+}
+
+auto CompilerThreadPool::dequeue(program_token_t const& token) -> Job {
+    std::unique_lock const lock(mQueueLock);
+    Job job;
+    auto&& [q, pos] = find(token);
+    if (pos != q.end()) {
+        std::swap(job, pos->second);
+        q.erase(pos);
+    }
+    return job;
+}
+
+void CompilerThreadPool::queue(CompilerPriorityQueue priorityQueue,
+        program_token_t const& token, Job&& job) {
+    std::unique_lock const lock(mQueueLock);
+    mQueues[size_t(priorityQueue)].emplace_back(token, std::move(job));
+    mQueueCondition.notify_one();
+}
+
+void CompilerThreadPool::terminate() noexcept {
+    std::unique_lock lock(mQueueLock);
+    mExitRequested = true;
+    mQueueCondition.notify_all();
+    lock.unlock();
+
+    for (auto& thread: mCompilerThreads) {
+        if (thread.joinable()) {
+            thread.join();
+        }
+    }
+    mCompilerThreads.clear();
+
+    // Clear all the queues, dropping the remaining jobs. This relies on the jobs being cancelable.
+    for (auto&& q : mQueues) {
+        q.clear();
+    }
+}
+
+} // namespace filament::backend