diff --git a/lib/include/srsran/srslog/detail/log_backend.h b/lib/include/srsran/srslog/detail/log_backend.h index d1765b498..5af3ec13a 100644 --- a/lib/include/srsran/srslog/detail/log_backend.h +++ b/lib/include/srsran/srslog/detail/log_backend.h @@ -14,6 +14,7 @@ #define SRSLOG_DETAIL_LOG_BACKEND_H #include "srsran/srslog/bundled/fmt/printf.h" +#include "srsran/srslog/shared_types.h" namespace srslog { @@ -31,7 +32,7 @@ public: /// Starts the processing of incoming log entries. /// NOTE: Calling this function more than once has no side effects. - virtual void start() = 0; + virtual void start(backend_priority priority = backend_priority::normal) = 0; /// Allocates a dyn_arg_store and returns a pointer to it on success, otherwise returns nullptr. virtual fmt::dynamic_format_arg_store* alloc_arg_store() = 0; diff --git a/lib/include/srsran/srslog/detail/support/work_queue.h b/lib/include/srsran/srslog/detail/support/work_queue.h index 00b29721e..ffe32735f 100644 --- a/lib/include/srsran/srslog/detail/support/work_queue.h +++ b/lib/include/srsran/srslog/detail/support/work_queue.h @@ -28,7 +28,7 @@ template class work_queue { srsran::dyn_circular_buffer queue; - mutable condition_variable cond_var; + mutable mutex m; static constexpr size_t threshold = capacity * 0.98; public: @@ -41,15 +41,14 @@ public: /// queue is full, otherwise true. bool push(const T& value) { - cond_var.lock(); + m.lock(); // Discard the new element if we reach the maximum capacity. if (queue.full()) { - cond_var.unlock(); + m.unlock(); return false; } queue.push(value); - cond_var.unlock(); - cond_var.signal(); + m.unlock(); return true; } @@ -58,56 +57,26 @@ public: /// queue is full, otherwise true. bool push(T&& value) { - cond_var.lock(); + m.lock(); // Discard the new element if we reach the maximum capacity. if (queue.full()) { - cond_var.unlock(); + m.unlock(); return false; } queue.push(std::move(value)); - cond_var.unlock(); - cond_var.signal(); + m.unlock(); return true; } - /// Extracts the top most element from the queue. - /// NOTE: This method blocks while the queue is empty. - T pop() + /// Extracts the top most element from the queue if it exists. + /// Returns a pair with a bool indicating if the pop has been successful. + std::pair try_pop() { - cond_var.lock(); + m.lock(); - while (queue.empty()) { - cond_var.wait(); - } - - T elem = std::move(queue.top()); - queue.pop(); - - cond_var.unlock(); - - return elem; - } - - /// Extracts the top most element from the queue. - /// NOTE: This method blocks while the queue is empty or or until the - /// programmed timeout expires. Returns a pair with a bool indicating if the - /// pop has been successful. - std::pair timed_pop(unsigned timeout_ms) - { - // Build an absolute time reference for the expiration time. - timespec ts = condition_variable::build_timeout(timeout_ms); - - cond_var.lock(); - - bool timedout = false; - while (queue.empty() && !timedout) { - timedout = cond_var.wait(ts); - } - - // Did we wake up on timeout? - if (timedout && queue.empty()) { - cond_var.unlock(); + if (queue.empty()) { + m.unlock(); return {false, T()}; } @@ -115,7 +84,7 @@ public: T Item = std::move(queue.top()); queue.pop(); - cond_var.unlock(); + m.unlock(); return {true, std::move(Item)}; } @@ -126,7 +95,7 @@ public: /// Returns true when the queue is almost full, otherwise returns false. bool is_almost_full() const { - cond_var_scoped_lock lock(cond_var); + scoped_lock lock(m); return queue.size() > threshold; } diff --git a/lib/include/srsran/srslog/shared_types.h b/lib/include/srsran/srslog/shared_types.h index 0598c59dd..c508219ef 100644 --- a/lib/include/srsran/srslog/shared_types.h +++ b/lib/include/srsran/srslog/shared_types.h @@ -20,6 +20,17 @@ namespace srslog { /// Generic error handler callback. using error_handler = std::function; +/// Backend priority levels. +enum class backend_priority +{ + /// Default priority of the operating system. + normal, + /// Thread will be given a high priority. + high, + /// Thread will be given a very high priority. + very_high +}; + } // namespace srslog #endif // SRSLOG_SHARED_TYPES_H diff --git a/lib/include/srsran/srslog/srslog.h b/lib/include/srsran/srslog/srslog.h index 9de919ceb..632d38a91 100644 --- a/lib/include/srsran/srslog/srslog.h +++ b/lib/include/srsran/srslog/srslog.h @@ -223,7 +223,7 @@ sink* create_stderr_sink(const std::string& name = "stderr"); /// This function initializes the logging framework. It must be called before /// any log entry is generated. /// NOTE: Calling this function more than once has no side effects. -void init(); +void init(backend_priority priority = backend_priority::normal); /// Flushes the contents of all the registered sinks. The caller thread will /// block until the operation is completed. diff --git a/lib/src/srslog/backend_worker.cpp b/lib/src/srslog/backend_worker.cpp index a564b69fe..31bbc6e59 100644 --- a/lib/src/srslog/backend_worker.cpp +++ b/lib/src/srslog/backend_worker.cpp @@ -24,12 +24,48 @@ void backend_worker::stop() } } -void backend_worker::create_worker() +void backend_worker::set_thread_priority(backend_priority priority) const +{ + switch (priority) { + case backend_priority::normal: + break; + case backend_priority::high: { + int min = ::sched_get_priority_min(SCHED_FIFO); + if (min == -1) { + err_handler("Unable to set the backend thread priority to high, falling back to normal priority."); + return; + } + ::sched_param sch{min}; + if (::pthread_setschedparam(::pthread_self(), SCHED_FIFO, &sch)) { + err_handler("Unable to set the backend thread priority to high, falling back to normal priority."); + return; + } + break; + } + case backend_priority::very_high: { + int max = ::sched_get_priority_max(SCHED_FIFO); + int min = ::sched_get_priority_min(SCHED_FIFO); + if (max == -1 || min == -1) { + err_handler("Unable to set the backend thread priority to real time, falling back to normal priority."); + return; + } + ::sched_param sch{min + ((max - min) / 2)}; + if (::pthread_setschedparam(::pthread_self(), SCHED_FIFO, &sch)) { + err_handler("Unable to set the backend thread priority to real time, falling back to normal priority."); + return; + } + break; + } + } +} + +void backend_worker::create_worker(backend_priority priority) { assert(!running_flag && "Only one worker thread should be created"); - std::thread t([this]() { + std::thread t([this, priority]() { running_flag = true; + set_thread_priority(priority); do_work(); }); @@ -41,21 +77,26 @@ void backend_worker::create_worker() } } -void backend_worker::start() +void backend_worker::start(backend_priority priority) { // Ensure we only create the worker thread once. - std::call_once(start_once_flag, [this]() { create_worker(); }); + std::call_once(start_once_flag, [this, priority]() { create_worker(priority); }); } void backend_worker::do_work() { assert(running_flag && "Thread entry function called without running thread"); + /// This period defines the time the worker will sleep while waiting for new entries. This is required to check the + /// termination variable periodically. + constexpr std::chrono::microseconds sleep_period{100}; + while (running_flag) { - auto item = queue.timed_pop(sleep_period_ms); + auto item = queue.try_pop(); - // Spin again when the timeout expires. + // Spin while there are no new entries to process. if (!item.first) { + std::this_thread::sleep_for(sleep_period); continue; } @@ -113,7 +154,7 @@ void backend_worker::process_outstanding_entries() assert(!running_flag && "Cannot process outstanding entries while thread is running"); while (true) { - auto item = queue.timed_pop(1); + auto item = queue.try_pop(); // Check if the queue is empty. if (!item.first) { diff --git a/lib/src/srslog/backend_worker.h b/lib/src/srslog/backend_worker.h index e45786dab..9c3992331 100644 --- a/lib/src/srslog/backend_worker.h +++ b/lib/src/srslog/backend_worker.h @@ -26,11 +26,6 @@ namespace srslog { /// log entries from a work queue and dispatches them to the selected sinks. class backend_worker { - /// This period defines the maximum time the worker will sleep while waiting - /// for new entries. This is required to check the termination variable - /// periodically. - static constexpr unsigned sleep_period_ms = 500; - public: backend_worker(detail::work_queue& queue, detail::dyn_arg_store_pool& arg_pool) : queue(queue), arg_pool(arg_pool), running_flag(false) @@ -44,7 +39,7 @@ public: /// Starts the backend worker thread. After returning from this function the /// secondary thread is ensured to be running. Calling this function more than /// once has no effect. - void start(); + void start(backend_priority priority); /// Stops the backend worker thread if it is running, otherwise the call has /// no effect. After returning from this function the secondary thread is @@ -78,7 +73,7 @@ public: private: /// Creates the worker thread. /// NOTE: This function should be only called once. - void create_worker(); + void create_worker(backend_priority priority); /// Entry function used by the secondary thread. void do_work(); @@ -103,6 +98,9 @@ private: } } + /// Establishes the specified thread priority for the calling thread. + void set_thread_priority(backend_priority priority) const; + private: detail::work_queue& queue; detail::dyn_arg_store_pool& arg_pool; diff --git a/lib/src/srslog/log_backend_impl.h b/lib/src/srslog/log_backend_impl.h index 23ca4b215..ed959a2ab 100644 --- a/lib/src/srslog/log_backend_impl.h +++ b/lib/src/srslog/log_backend_impl.h @@ -29,7 +29,7 @@ public: log_backend_impl(const log_backend_impl& other) = delete; log_backend_impl& operator=(const log_backend_impl& other) = delete; - void start() override { worker.start(); } + void start(backend_priority priority = backend_priority::normal) override { worker.start(priority); } bool push(detail::log_entry&& entry) override { diff --git a/lib/src/srslog/srslog.cpp b/lib/src/srslog/srslog.cpp index d223b1f0f..b50e6c627 100644 --- a/lib/src/srslog/srslog.cpp +++ b/lib/src/srslog/srslog.cpp @@ -181,9 +181,9 @@ bool srslog::install_custom_sink(const std::string& id, std::unique_ptr s) /// Framework configuration and control function implementations. /// -void srslog::init() +void srslog::init(backend_priority priority) { - srslog_instance::get().get_backend().start(); + srslog_instance::get().get_backend().start(priority); } void srslog::flush() diff --git a/lib/test/srslog/CMakeLists.txt b/lib/test/srslog/CMakeLists.txt index 7859d3d23..46a59303e 100644 --- a/lib/test/srslog/CMakeLists.txt +++ b/lib/test/srslog/CMakeLists.txt @@ -6,6 +6,9 @@ # the distribution. # +add_executable(srslog_frontend_latency benchmarks/frontend_latency.cpp) +target_link_libraries(srslog_frontend_latency srslog) + add_executable(srslog_test srslog_test.cpp) target_link_libraries(srslog_test srslog) add_test(srslog_test srslog_test) diff --git a/lib/test/srslog/benchmarks/frontend_latency.cpp b/lib/test/srslog/benchmarks/frontend_latency.cpp new file mode 100644 index 000000000..2866055bc --- /dev/null +++ b/lib/test/srslog/benchmarks/frontend_latency.cpp @@ -0,0 +1,137 @@ +/** + * + * \section COPYRIGHT + * + * Copyright 2013-2021 Software Radio Systems Limited + * + * By using this file, you agree to the terms and conditions set + * forth in the LICENSE file which can be found at the top level of + * the distribution. + * + */ + +#include "srsran/srslog/srslog.h" +#include +#include +#include + +using namespace srslog; + +static constexpr unsigned num_iterations = 4000; +static constexpr unsigned num_entries_per_iter = 40; + +namespace { + +/// This helper class checks if there has been context switches between its construction and destruction for the caller +/// thread. +class context_switch_checker +{ +public: + explicit context_switch_checker(std::atomic& counter) : counter(counter) + { + ::getrusage(RUSAGE_THREAD, &before); + } + + ~context_switch_checker() + { + ::rusage after{}; + ::getrusage(RUSAGE_THREAD, &after); + unsigned diff = (after.ru_nvcsw - before.ru_nvcsw) + (after.ru_nivcsw - before.ru_nivcsw); + if (diff) { + counter.fetch_add(diff, std::memory_order_relaxed); + } + } + +private: + ::rusage before{}; + std::atomic& counter; +}; + +} // namespace + +/// Busy waits in the calling thread for the specified amount of time. +static void busy_wait(std::chrono::milliseconds interval) +{ + auto begin = std::chrono::steady_clock::now(); + auto end = begin + interval; + + while (std::chrono::steady_clock::now() < end) { + } +} + +/// Worker function used for each thread of the benchmark to generate and measure the time taken for each log entry. +static void run_thread(log_channel& c, std::vector& results, std::atomic& ctx_counter) +{ + for (unsigned iter = 0; iter != num_iterations; ++iter) { + context_switch_checker ctx_checker(ctx_counter); + + auto begin = std::chrono::steady_clock::now(); + for (unsigned entry_num = 0; entry_num != num_entries_per_iter; ++entry_num) { + double d = entry_num; + c("SRSLOG latency benchmark: int: %u, double: %f, string: %s", iter, d, "test"); + } + auto end = std::chrono::steady_clock::now(); + + results.push_back(std::chrono::duration_cast(end - begin).count() / num_entries_per_iter); + + busy_wait(std::chrono::milliseconds(4)); + } +} + +/// This function runs the latency benchmark generating log entries using the specified number of threads. +static void benchmark(unsigned num_threads) +{ + std::vector > thread_results; + thread_results.resize(num_threads); + for (auto& v : thread_results) { + v.reserve(num_iterations); + } + + auto& s = srslog::fetch_file_sink("srslog_latency_benchmark.txt"); + auto& channel = srslog::fetch_log_channel("bench", s, {}); + + srslog::init(); + + std::vector workers; + workers.reserve(num_threads); + + std::atomic ctx_counter(0); + for (unsigned i = 0; i != num_threads; ++i) { + workers.emplace_back(run_thread, std::ref(channel), std::ref(thread_results[i]), std::ref(ctx_counter)); + } + for (auto& w : workers) { + w.join(); + } + + std::vector results; + results.reserve(num_threads * num_iterations); + for (const auto& v : thread_results) { + results.insert(results.end(), v.begin(), v.end()); + } + std::sort(results.begin(), results.end()); + + fmt::print("SRSLOG Frontend Latency Benchmark - logging with {} thread{}\n" + "All values in nanoseconds\n" + "Percentiles: | 50th | 75th | 90th | 99th | 99.9th | Worst |\n" + " |{:6}|{:6}|{:6}|{:6}|{:8}|{:7}|\n" + "Context switches: {} in {} of generated entries\n\n", + num_threads, + (num_threads > 1) ? "s" : "", + results[static_cast(results.size() * 0.5)], + results[static_cast(results.size() * 0.75)], + results[static_cast(results.size() * 0.9)], + results[static_cast(results.size() * 0.99)], + results[static_cast(results.size() * 0.999)], + results.back(), + ctx_counter, + num_threads * num_iterations * num_entries_per_iter); +} + +int main() +{ + for (auto n : {1, 2, 4}) { + benchmark(n); + } + + return 0; +} diff --git a/lib/test/srslog/event_trace_test.cpp b/lib/test/srslog/event_trace_test.cpp index d55648e08..df5b0c16a 100644 --- a/lib/test/srslog/event_trace_test.cpp +++ b/lib/test/srslog/event_trace_test.cpp @@ -25,7 +25,7 @@ namespace { class backend_spy : public detail::log_backend { public: - void start() override {} + void start(srslog::backend_priority priority) override {} bool push(detail::log_entry&& entry) override { diff --git a/lib/test/srslog/log_channel_test.cpp b/lib/test/srslog/log_channel_test.cpp index af231903b..c5674b4e8 100644 --- a/lib/test/srslog/log_channel_test.cpp +++ b/lib/test/srslog/log_channel_test.cpp @@ -60,7 +60,7 @@ namespace { class backend_spy : public detail::log_backend { public: - void start() override {} + void start(srslog::backend_priority priority) override {} bool push(detail::log_entry&& entry) override { diff --git a/lib/test/srslog/test_dummies.h b/lib/test/srslog/test_dummies.h index 412f1e42b..9f546219b 100644 --- a/lib/test/srslog/test_dummies.h +++ b/lib/test/srslog/test_dummies.h @@ -14,6 +14,7 @@ #define TEST_DUMMIES #include "srsran/srslog/detail/log_backend.h" +#include "srsran/srslog/shared_types.h" #include "srsran/srslog/sink.h" namespace test_dummies { @@ -67,7 +68,7 @@ public: class backend_dummy : public srslog::detail::log_backend { public: - void start() override {} + void start(srslog::backend_priority priority) override {} bool push(srslog::detail::log_entry&& entry) override { return true; }