Merge #18011: Replace current benchmarking framework with nanobench

78c312c983 Replace current benchmarking framework with nanobench (Martin Ankerl)

Pull request description:

  Replace current benchmarking framework with nanobench

  This replaces the current benchmarking framework with nanobench [1], an
  MIT licensed single-header benchmarking library, of which I am the
  autor. This has in my opinion several advantages, especially on Linux:

  * fast: Running all benchmarks takes ~6 seconds instead of 4m13s on
    an Intel i7-8700 CPU @ 3.20GHz.

  * accurate: I ran e.g. the benchmark for SipHash_32b 10 times and
    calculate standard deviation / mean = coefficient of variation:

    * 0.57% CV for old benchmarking framework
    * 0.20% CV for nanobench

    So the benchmark results with nanobench seem to vary less than with
    the old framework.

  * It automatically determines runtime based on clock precision, no need
    to specify number of evaluations.

  * measure instructions, cycles, branches, instructions per cycle,
    branch misses (only Linux, when performance counters are available)

  * output in markdown table format.

  * Warn about unstable environment (frequency scaling, turbo, ...)

  * For better profiling, it is possible to set the environment variable
    NANOBENCH_ENDLESS to force endless running of a particular benchmark
    without the need to recompile. This makes it to e.g. run "perf top"
    and look at hotspots.

  Here is an example copy & pasted from the terminal output:

  |             ns/byte |              byte/s |    err% |        ins/byte |        cyc/byte |    IPC |       bra/byte |   miss% |     total | benchmark
  |--------------------:|--------------------:|--------:|----------------:|----------------:|-------:|---------------:|--------:|----------:|:----------
  |                2.52 |      396,529,415.94 |    0.6% |           25.42 |            8.02 |  3.169 |           0.06 |    0.0% |      0.03 | `bench/crypto_hash.cpp RIPEMD160`
  |                1.87 |      535,161,444.83 |    0.3% |           21.36 |            5.95 |  3.589 |           0.06 |    0.0% |      0.02 | `bench/crypto_hash.cpp SHA1`
  |                3.22 |      310,344,174.79 |    1.1% |           36.80 |           10.22 |  3.601 |           0.09 |    0.0% |      0.04 | `bench/crypto_hash.cpp SHA256`
  |                2.01 |      496,375,796.23 |    0.0% |           18.72 |            6.43 |  2.911 |           0.01 |    1.0% |      0.00 | `bench/crypto_hash.cpp SHA256D64_1024`
  |                7.23 |      138,263,519.35 |    0.1% |           82.66 |           23.11 |  3.577 |           1.63 |    0.1% |      0.00 | `bench/crypto_hash.cpp SHA256_32b`
  |                3.04 |      328,780,166.40 |    0.3% |           35.82 |            9.69 |  3.696 |           0.03 |    0.0% |      0.03 | `bench/crypto_hash.cpp SHA512`

  [1] https://github.com/martinus/nanobench

ACKs for top commit:
  laanwj:
    ACK 78c312c983

Tree-SHA512: 9e18770b18b6f95a7d0105a4a5497d31cf4eb5efe6574f4482f6f1b4c88d7e0946b9a4a1e9e8e6ecbf41a3f2d7571240677dcb45af29a6f0584e89b25f32e49e

doc/benchmarking.md

@@ -19,8 +19,10 @@ After compiling bitcoin-core, the benchmarks can be run with:
 
 The output will look similar to:
 ```
-# Benchmark, evals, iterations, total, min, max, median
-AssembleBlock, 5, 700, 1.79954, 0.000510913, 0.000517018, 0.000514497
+|             ns/byte |              byte/s | error % | benchmark
+|--------------------:|--------------------:|--------:|:----------------------------------------------
+|               64.13 |       15,592,356.01 |    0.1% | `Base58CheckEncode`
+|               24.56 |       40,722,672.68 |    0.2% | `Base58Decode`
 ...
 ```