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authorvitalyisaev <vitalyisaev@yandex-team.com>2023-06-29 10:00:50 +0300
committervitalyisaev <vitalyisaev@yandex-team.com>2023-06-29 10:00:50 +0300
commit6ffe9e53658409f212834330e13564e4952558f6 (patch)
tree85b1e00183517648b228aafa7c8fb07f5276f419 /contrib/libs/llvm14/lib/Support/Parallel.cpp
parent726057070f9c5a91fc10fde0d5024913d10f1ab9 (diff)
downloadydb-6ffe9e53658409f212834330e13564e4952558f6.tar.gz
YQ Connector: support managed ClickHouse
Со стороны dqrun можно обратиться к инстансу коннектора, который работает на streaming стенде, и извлечь данные из облачного CH.
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+//===- llvm/Support/Parallel.cpp - Parallel algorithms --------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Parallel.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Threading.h"
+
+#include <atomic>
+#include <future>
+#include <stack>
+#include <thread>
+#include <vector>
+
+llvm::ThreadPoolStrategy llvm::parallel::strategy;
+
+#if LLVM_ENABLE_THREADS
+
+namespace llvm {
+namespace parallel {
+namespace detail {
+
+namespace {
+
+/// An abstract class that takes closures and runs them asynchronously.
+class Executor {
+public:
+ virtual ~Executor() = default;
+ virtual void add(std::function<void()> func) = 0;
+
+ static Executor *getDefaultExecutor();
+};
+
+/// An implementation of an Executor that runs closures on a thread pool
+/// in filo order.
+class ThreadPoolExecutor : public Executor {
+public:
+ explicit ThreadPoolExecutor(ThreadPoolStrategy S = hardware_concurrency()) {
+ unsigned ThreadCount = S.compute_thread_count();
+ // Spawn all but one of the threads in another thread as spawning threads
+ // can take a while.
+ Threads.reserve(ThreadCount);
+ Threads.resize(1);
+ std::lock_guard<std::mutex> Lock(Mutex);
+ Threads[0] = std::thread([this, ThreadCount, S] {
+ for (unsigned I = 1; I < ThreadCount; ++I) {
+ Threads.emplace_back([=] { work(S, I); });
+ if (Stop)
+ break;
+ }
+ ThreadsCreated.set_value();
+ work(S, 0);
+ });
+ }
+
+ void stop() {
+ {
+ std::lock_guard<std::mutex> Lock(Mutex);
+ if (Stop)
+ return;
+ Stop = true;
+ }
+ Cond.notify_all();
+ ThreadsCreated.get_future().wait();
+ }
+
+ ~ThreadPoolExecutor() override {
+ stop();
+ std::thread::id CurrentThreadId = std::this_thread::get_id();
+ for (std::thread &T : Threads)
+ if (T.get_id() == CurrentThreadId)
+ T.detach();
+ else
+ T.join();
+ }
+
+ struct Creator {
+ static void *call() { return new ThreadPoolExecutor(strategy); }
+ };
+ struct Deleter {
+ static void call(void *Ptr) { ((ThreadPoolExecutor *)Ptr)->stop(); }
+ };
+
+ void add(std::function<void()> F) override {
+ {
+ std::lock_guard<std::mutex> Lock(Mutex);
+ WorkStack.push(F);
+ }
+ Cond.notify_one();
+ }
+
+private:
+ void work(ThreadPoolStrategy S, unsigned ThreadID) {
+ S.apply_thread_strategy(ThreadID);
+ while (true) {
+ std::unique_lock<std::mutex> Lock(Mutex);
+ Cond.wait(Lock, [&] { return Stop || !WorkStack.empty(); });
+ if (Stop)
+ break;
+ auto Task = WorkStack.top();
+ WorkStack.pop();
+ Lock.unlock();
+ Task();
+ }
+ }
+
+ std::atomic<bool> Stop{false};
+ std::stack<std::function<void()>> WorkStack;
+ std::mutex Mutex;
+ std::condition_variable Cond;
+ std::promise<void> ThreadsCreated;
+ std::vector<std::thread> Threads;
+};
+
+Executor *Executor::getDefaultExecutor() {
+ // The ManagedStatic enables the ThreadPoolExecutor to be stopped via
+ // llvm_shutdown() which allows a "clean" fast exit, e.g. via _exit(). This
+ // stops the thread pool and waits for any worker thread creation to complete
+ // but does not wait for the threads to finish. The wait for worker thread
+ // creation to complete is important as it prevents intermittent crashes on
+ // Windows due to a race condition between thread creation and process exit.
+ //
+ // The ThreadPoolExecutor will only be destroyed when the static unique_ptr to
+ // it is destroyed, i.e. in a normal full exit. The ThreadPoolExecutor
+ // destructor ensures it has been stopped and waits for worker threads to
+ // finish. The wait is important as it prevents intermittent crashes on
+ // Windows when the process is doing a full exit.
+ //
+ // The Windows crashes appear to only occur with the MSVC static runtimes and
+ // are more frequent with the debug static runtime.
+ //
+ // This also prevents intermittent deadlocks on exit with the MinGW runtime.
+
+ static ManagedStatic<ThreadPoolExecutor, ThreadPoolExecutor::Creator,
+ ThreadPoolExecutor::Deleter>
+ ManagedExec;
+ static std::unique_ptr<ThreadPoolExecutor> Exec(&(*ManagedExec));
+ return Exec.get();
+}
+} // namespace
+
+static std::atomic<int> TaskGroupInstances;
+
+// Latch::sync() called by the dtor may cause one thread to block. If is a dead
+// lock if all threads in the default executor are blocked. To prevent the dead
+// lock, only allow the first TaskGroup to run tasks parallelly. In the scenario
+// of nested parallel_for_each(), only the outermost one runs parallelly.
+TaskGroup::TaskGroup() : Parallel(TaskGroupInstances++ == 0) {}
+TaskGroup::~TaskGroup() {
+ // We must ensure that all the workloads have finished before decrementing the
+ // instances count.
+ L.sync();
+ --TaskGroupInstances;
+}
+
+void TaskGroup::spawn(std::function<void()> F) {
+ if (Parallel) {
+ L.inc();
+ Executor::getDefaultExecutor()->add([&, F] {
+ F();
+ L.dec();
+ });
+ } else {
+ F();
+ }
+}
+
+} // namespace detail
+} // namespace parallel
+} // namespace llvm
+#endif // LLVM_ENABLE_THREADS
+
+void llvm::parallelForEachN(size_t Begin, size_t End,
+ llvm::function_ref<void(size_t)> Fn) {
+ // If we have zero or one items, then do not incur the overhead of spinning up
+ // a task group. They are surprisingly expensive, and because they do not
+ // support nested parallelism, a single entry task group can block parallel
+ // execution underneath them.
+#if LLVM_ENABLE_THREADS
+ auto NumItems = End - Begin;
+ if (NumItems > 1 && parallel::strategy.ThreadsRequested != 1) {
+ // Limit the number of tasks to MaxTasksPerGroup to limit job scheduling
+ // overhead on large inputs.
+ auto TaskSize = NumItems / parallel::detail::MaxTasksPerGroup;
+ if (TaskSize == 0)
+ TaskSize = 1;
+
+ parallel::detail::TaskGroup TG;
+ for (; Begin + TaskSize < End; Begin += TaskSize) {
+ TG.spawn([=, &Fn] {
+ for (size_t I = Begin, E = Begin + TaskSize; I != E; ++I)
+ Fn(I);
+ });
+ }
+ for (; Begin != End; ++Begin)
+ Fn(Begin);
+ return;
+ }
+#endif
+
+ for (; Begin != End; ++Begin)
+ Fn(Begin);
+}