flowbench is an executable that can be used to microbenchmark parts of the FoundationDB code. The goal is to make it easy to test the performance of various sub-millisecond operations using flow and fdbrpc. Specifically, this tool can be used to:

Test the performance effects of changes to the actor compiler or to the flow and fdbrpc libraries
Test the performance of various uses of the flow and fdbrpc libraries
Find areas for improvement in the flow and fdbrpc libraries
Compare flow/fdbrpc primitives to alternatives provided by the standard library or other third-party libraries.

Usage

To build the flowbench executable, run ninja flowbench or make flowbench depending on which build system you're using.
Then you can run bin/flowbench --help to see possible uses of flowbench.
Running bin/flowbench directly will run all registered benchmarks, but you may want to limit your run to a subset of benchmarks. This can be done by running bin/flowbench --benchmark_filter=<regex>
All benchmark names can be listed with bin/flowbench --benchmark_list_tests
Example output:

$ bin/flowbench --benchmark_filter=bench_ref
2020-08-04 21:49:40
Running bin/flowbench
Run on (7 X 2904 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x7)
  L1 Instruction 32 KiB (x7)
  L2 Unified 256 KiB (x7)
  L3 Unified 12288 KiB (x1)
Load Average: 0.15, 0.15, 0.72
---------------------------------------------------------------------------------------------------------------
Benchmark                                                     Time             CPU   Iterations UserCounters...
---------------------------------------------------------------------------------------------------------------
bench_ref_create_and_destroy<RefType::RawPointer>          4.90 ns         4.90 ns    116822124 items_per_second=203.88M/s
bench_ref_create_and_destroy<RefType::UniquePointer>       4.94 ns         4.94 ns    141101924 items_per_second=202.555M/s
bench_ref_create_and_destroy<RefType::SharedPointer>       42.5 ns         42.5 ns     13802909 items_per_second=23.531M/s
bench_ref_create_and_destroy<RefType::FlowReference>       5.05 ns         5.05 ns    100000000 items_per_second=197.955M/s
bench_ref_copy<RefType::RawPointer>                        1.15 ns         1.15 ns    612121585 items_per_second=871.218M/s
bench_ref_copy<RefType::SharedPointer>                     10.0 ns         10.0 ns     67553102 items_per_second=99.8113M/s
bench_ref_copy<RefType::FlowReference>                     2.33 ns         2.33 ns    292317474 items_per_second=428.507M/s

More detailed documentation can be found at https://github.com/google/benchmark

Existing Benchmarks

bench_populate measures the population of a vector of mutations
bench_ref compares the performance of the flow Reference type to other pointer types
bench_iterate measures iteration over a list of mutations
bench_stream measures the performance of writing to and reading from a PromiseStream
bench_random measures the performance of DeterministicRandom.
bench_timer measures the performance of FoundationDB timers.

Future use cases

Benchmark the overhead of sending and receiving messages through FlowTransport
Benchmark the performance of serializing/deserializing various types