Boost C++ Libraries

Performance measurements were taken using std::chrono::highresolution_clock, with overhead corrections. The code was compiled with gcc-6.20, using build options: variant = release, optimization = speed. Tests were executed on Intel Core i7-4770S 3.10GHz, 4 cores with 8 hyperthreads (4C/8T), running Linux (4.7.0/x86_64).

Measurements headed 1C/1T were run in a single-threaded process.

The microbenchmark syknet from Alexander Temerev was ported and used for performance measurements. At the root the test spawns 10 threads-of-execution (ToE), e.g. actor/goroutine/fiber etc.. Each spawned ToE spawns additional 10 ToEs ... until 100000 ToEs are created. ToEs return back ther ordinal numbers (0 ... 99999), which are summed on the previous level and sent back upstream, until reaching the root. The test was run 10-20 times, producing a range of values for each measurement.

std::thread can not be tested at this time (C++14) because the API does not allow to set thread stack size (idefault on Linux 2MB, on Windows 1MB). An out-of-memory error is likely. With pthreads the stack size is set 8kBC.

The test utilizes 4 cores with Symmetric MultiThreading enabled (8 logical CPUs). The fiber stacks are allocated by fixedsize_stack.

As the benchmark shows, the memory allocation algorithm is significant for performance in a multithreaded environment. The tests use glibc’s memory allocation algorithm (based on ptmalloc2) as well as Google’s TCmalloc (via linkflags="-ltcmalloc").^[9]

The shared_work scheduling algorithm uses one global queue, containing fibers ready to run, shared between all threads. The work is distributed equally over all threads. In the work_stealing scheduling algorithm, each thread has its own local queue. Fibers that are ready to run are pushed to and popped from the local queue. If the queue runs out of ready fibers, fibers are stolen from the local queues of other participating threads.