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diff --git a/benchmark/writing-and-running-benchmarks.md b/benchmark/writing-and-running-benchmarks.md new file mode 100644 index 0000000000..6097830aee --- /dev/null +++ b/benchmark/writing-and-running-benchmarks.md @@ -0,0 +1,475 @@ +# How to Write and Run Benchmarks in Node.js Core + +## Table of Contents + +* [Prerequisites](#prerequisites) + * [HTTP Benchmark Requirements](#http-benchmark-requirements) + * [Benchmark Analysis Requirements](#benchmark-analysis-requirements) +* [Running benchmarks](#running-benchmarks) + * [Running individual benchmarks](#running-individual-benchmarks) + * [Running all benchmarks](#running-all-benchmarks) + * [Comparing Node.js versions](#comparing-nodejs-versions) + * [Comparing parameters](#comparing-parameters) + * [Running Benchmarks on the CI](#running-benchmarks-on-the-ci) +* [Creating a benchmark](#creating-a-benchmark) + * [Basics of a benchmark](#basics-of-a-benchmark) + * [Creating an HTTP benchmark](#creating-an-http-benchmark) + +## Prerequisites + +Basic Unix tools are required for some benchmarks. +[Git for Windows][git-for-windows] includes Git Bash and the necessary tools, +which need to be included in the global Windows `PATH`. + +### HTTP Benchmark Requirements + +Most of the HTTP benchmarks require a benchmarker to be installed. This can be +either [`wrk`][wrk] or [`autocannon`][autocannon]. + +`Autocannon` is a Node.js script that can be installed using +`npm install -g autocannon`. It will use the Node.js executable that is in the +path. In order to compare two HTTP benchmark runs, make sure that the +Node.js version in the path is not altered. + +`wrk` may be available through one of the available package managers. If not, +it can be easily built [from source][wrk] via `make`. + +By default, `wrk` will be used as the benchmarker. If it is not available, +`autocannon` will be used in its place. When creating an HTTP benchmark, the +benchmarker to be used should be specified by providing it as an argument: + +`node benchmark/run.js --set benchmarker=autocannon http` + +`node benchmark/http/simple.js benchmarker=autocannon` + +#### HTTP/2 Benchmark Requirements + +To run the `http2` benchmarks, the `h2load` benchmarker must be used. The +`h2load` tool is a component of the `nghttp2` project and may be installed +from [nghttp2.org][] or built from source. + +`node benchmark/http2/simple.js benchmarker=autocannon` + +### Benchmark Analysis Requirements + +To analyze the results, `R` should be installed. Use one of the available +package managers or download it from https://www.r-project.org/. + +The R packages `ggplot2` and `plyr` are also used and can be installed using +the R REPL. + +```R +$ R +install.packages("ggplot2") +install.packages("plyr") +``` + +In the event that a message is reported stating that a CRAN mirror must be +selected first, specify a mirror by adding in the repo parameter. + +If we used the "http://cran.us.r-project.org" mirror, it could look something +like this: + +```R +install.packages("ggplot2", repo="http://cran.us.r-project.org") +``` + +Of course, use an appropriate mirror based on location. +A list of mirrors is [located here](https://cran.r-project.org/mirrors.html). + +## Running benchmarks + +### Running individual benchmarks + +This can be useful for debugging a benchmark or doing a quick performance +measure. But it does not provide the statistical information to make any +conclusions about the performance. + +Individual benchmarks can be executed by simply executing the benchmark script +with node. + +```console +$ node benchmark/buffers/buffer-tostring.js + +buffers/buffer-tostring.js n=10000000 len=0 arg=true: 62710590.393305704 +buffers/buffer-tostring.js n=10000000 len=1 arg=true: 9178624.591787899 +buffers/buffer-tostring.js n=10000000 len=64 arg=true: 7658962.8891432695 +buffers/buffer-tostring.js n=10000000 len=1024 arg=true: 4136904.4060201733 +buffers/buffer-tostring.js n=10000000 len=0 arg=false: 22974354.231509723 +buffers/buffer-tostring.js n=10000000 len=1 arg=false: 11485945.656765845 +buffers/buffer-tostring.js n=10000000 len=64 arg=false: 8718280.70650129 +buffers/buffer-tostring.js n=10000000 len=1024 arg=false: 4103857.0726124765 +``` + +Each line represents a single benchmark with parameters specified as +`${variable}=${value}`. Each configuration combination is executed in a separate +process. This ensures that benchmark results aren't affected by the execution +order due to V8 optimizations. **The last number is the rate of operations +measured in ops/sec (higher is better).** + +Furthermore a subset of the configurations can be specified, by setting them in +the process arguments: + +```console +$ node benchmark/buffers/buffer-tostring.js len=1024 + +buffers/buffer-tostring.js n=10000000 len=1024 arg=true: 3498295.68561504 +buffers/buffer-tostring.js n=10000000 len=1024 arg=false: 3783071.1678948295 +``` + +### Running all benchmarks + +Similar to running individual benchmarks, a group of benchmarks can be executed +by using the `run.js` tool. To see how to use this script, +run `node benchmark/run.js`. Again this does not provide the statistical +information to make any conclusions. + +```console +$ node benchmark/run.js assert + +assert/deepequal-buffer.js +assert/deepequal-buffer.js method="deepEqual" strict=0 len=100 n=20000: 773,200.4995493788 +assert/deepequal-buffer.js method="notDeepEqual" strict=0 len=100 n=20000: 964,411.712953848 +... + +assert/deepequal-map.js +assert/deepequal-map.js method="deepEqual_primitiveOnly" strict=0 len=500 n=500: 20,445.06368453332 +assert/deepequal-map.js method="deepEqual_objectOnly" strict=0 len=500 n=500: 1,393.3481642240833 +... + +assert/deepequal-object.js +assert/deepequal-object.js method="deepEqual" strict=0 size=100 n=5000: 1,053.1950937538475 +assert/deepequal-object.js method="notDeepEqual" strict=0 size=100 n=5000: 9,734.193251965213 +... +``` + +It is possible to execute more groups by adding extra process arguments. + +```console +$ node benchmark/run.js assert async_hooks +``` + +### Comparing Node.js versions + +To compare the effect of a new Node.js version use the `compare.js` tool. This +will run each benchmark multiple times, making it possible to calculate +statistics on the performance measures. To see how to use this script, +run `node benchmark/compare.js`. + +As an example on how to check for a possible performance improvement, the +[#5134](https://github.com/nodejs/node/pull/5134) pull request will be used as +an example. This pull request _claims_ to improve the performance of the +`string_decoder` module. + +First build two versions of Node.js, one from the master branch (here called +`./node-master`) and another with the pull request applied (here called +`./node-pr-5134`). + +To run multiple compiled versions in parallel you need to copy the output of the +build: `cp ./out/Release/node ./node-master`. Check out the following example: + +```console +$ git checkout master +$ ./configure && make -j4 +$ cp ./out/Release/node ./node-master + +$ git checkout pr-5134 +$ ./configure && make -j4 +$ cp ./out/Release/node ./node-pr-5134 +``` + +The `compare.js` tool will then produce a csv file with the benchmark results. + +```console +$ node benchmark/compare.js --old ./node-master --new ./node-pr-5134 string_decoder > compare-pr-5134.csv +``` + +*Tips: there are some useful options of `benchmark/compare.js`. For example, +if you want to compare the benchmark of a single script instead of a whole +module, you can use the `--filter` option:* + +```console + --new ./new-node-binary new node binary (required) + --old ./old-node-binary old node binary (required) + --runs 30 number of samples + --filter pattern string to filter benchmark scripts + --set variable=value set benchmark variable (can be repeated) + --no-progress don't show benchmark progress indicator +``` + +For analysing the benchmark results use the `compare.R` tool. + +```console +$ cat compare-pr-5134.csv | Rscript benchmark/compare.R + + confidence improvement accuracy (*) (**) (***) + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=128 encoding='ascii' *** -3.76 % ±1.36% ±1.82% ±2.40% + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=128 encoding='utf8' ** -0.81 % ±0.53% ±0.71% ±0.93% + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=32 encoding='ascii' *** -2.70 % ±0.83% ±1.11% ±1.45% + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=32 encoding='base64-ascii' *** -1.57 % ±0.83% ±1.11% ±1.46% +... +``` + +In the output, _improvement_ is the relative improvement of the new version, +hopefully this is positive. _confidence_ tells if there is enough +statistical evidence to validate the _improvement_. If there is enough evidence +then there will be at least one star (`*`), more stars is just better. **However +if there are no stars, then don't make any conclusions based on the +_improvement_.** Sometimes this is fine, for example if no improvements are +expected, then there shouldn't be any stars. + +**A word of caution:** Statistics is not a foolproof tool. If a benchmark shows +a statistical significant difference, there is a 5% risk that this +difference doesn't actually exist. For a single benchmark this is not an +issue. But when considering 20 benchmarks it's normal that one of them +will show significance, when it shouldn't. A possible solution is to instead +consider at least two stars (`**`) as the threshold, in that case the risk +is 1%. If three stars (`***`) is considered the risk is 0.1%. However this +may require more runs to obtain (can be set with `--runs`). + +_For the statistically minded, the R script performs an [independent/unpaired +2-group t-test][t-test], with the null hypothesis that the performance is the +same for both versions. The confidence field will show a star if the p-value +is less than `0.05`._ + +The `compare.R` tool can also produce a box plot by using the `--plot filename` +option. In this case there are 48 different benchmark combinations, and there +may be a need to filter the csv file. This can be done while benchmarking +using the `--set` parameter (e.g. `--set encoding=ascii`) or by filtering +results afterwards using tools such as `sed` or `grep`. In the `sed` case be +sure to keep the first line since that contains the header information. + +```console +$ cat compare-pr-5134.csv | sed '1p;/encoding='"'"ascii"'"'/!d' | Rscript benchmark/compare.R --plot compare-plot.png + + confidence improvement accuracy (*) (**) (***) + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=128 encoding='ascii' *** -3.76 % ±1.36% ±1.82% ±2.40% + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=32 encoding='ascii' *** -2.70 % ±0.83% ±1.11% ±1.45% + string_decoder/string-decoder.js n=2500000 chunkLen=16 inLen=4096 encoding='ascii' *** -4.06 % ±0.31% ±0.41% ±0.54% + string_decoder/string-decoder.js n=2500000 chunkLen=256 inLen=1024 encoding='ascii' *** -1.42 % ±0.58% ±0.77% ±1.01% +... +``` + +![compare tool boxplot](doc_img/compare-boxplot.png) + +### Comparing parameters + +It can be useful to compare the performance for different parameters, for +example to analyze the time complexity. + +To do this use the `scatter.js` tool, this will run a benchmark multiple times +and generate a csv with the results. To see how to use this script, +run `node benchmark/scatter.js`. + +```console +$ node benchmark/scatter.js benchmark/string_decoder/string-decoder.js > scatter.csv +``` + +After generating the csv, a comparison table can be created using the +`scatter.R` tool. Even more useful it creates an actual scatter plot when using +the `--plot filename` option. + +```console +$ cat scatter.csv | Rscript benchmark/scatter.R --xaxis chunkLen --category encoding --plot scatter-plot.png --log + +aggregating variable: inLen + +chunkLen encoding rate confidence.interval + 16 ascii 1515855.1 334492.68 + 16 base64-ascii 403527.2 89677.70 + 16 base64-utf8 322352.8 70792.93 + 16 utf16le 1714567.5 388439.81 + 16 utf8 1100181.6 254141.32 + 64 ascii 3550402.0 661277.65 + 64 base64-ascii 1093660.3 229976.34 + 64 base64-utf8 997804.8 227238.04 + 64 utf16le 3372234.0 647274.88 + 64 utf8 1731941.2 360854.04 + 256 ascii 5033793.9 723354.30 + 256 base64-ascii 1447962.1 236625.96 + 256 base64-utf8 1357269.2 231045.70 + 256 utf16le 4039581.5 655483.16 + 256 utf8 1828672.9 360311.55 + 1024 ascii 5677592.7 624771.56 + 1024 base64-ascii 1494171.7 227302.34 + 1024 base64-utf8 1399218.9 224584.79 + 1024 utf16le 4157452.0 630416.28 + 1024 utf8 1824266.6 359628.52 +``` + +Because the scatter plot can only show two variables (in this case _chunkLen_ +and _encoding_) the rest is aggregated. Sometimes aggregating is a problem, this +can be solved by filtering. This can be done while benchmarking using the +`--set` parameter (e.g. `--set encoding=ascii`) or by filtering results +afterwards using tools such as `sed` or `grep`. In the `sed` case be +sure to keep the first line since that contains the header information. + +```console +$ cat scatter.csv | sed -E '1p;/([^,]+, ){3}128,/!d' | Rscript benchmark/scatter.R --xaxis chunkLen --category encoding --plot scatter-plot.png --log + +chunkLen encoding rate confidence.interval + 16 ascii 1302078.5 71692.27 + 16 base64-ascii 338669.1 15159.54 + 16 base64-utf8 281904.2 20326.75 + 16 utf16le 1381515.5 58533.61 + 16 utf8 831183.2 33631.01 + 64 ascii 4363402.8 224030.00 + 64 base64-ascii 1036825.9 48644.72 + 64 base64-utf8 780059.3 60994.98 + 64 utf16le 3900749.5 158366.84 + 64 utf8 1723710.6 80665.65 + 256 ascii 8472896.1 511822.51 + 256 base64-ascii 2215884.6 104347.53 + 256 base64-utf8 1996230.3 131778.47 + 256 utf16le 5824147.6 234550.82 + 256 utf8 2019428.8 100913.36 + 1024 ascii 8340189.4 598855.08 + 1024 base64-ascii 2201316.2 111777.68 + 1024 base64-utf8 2002272.9 128843.11 + 1024 utf16le 5789281.7 240642.77 + 1024 utf8 2025551.2 81770.69 +``` + +![compare tool boxplot](doc_img/scatter-plot.png) + +### Running Benchmarks on the CI + +To see the performance impact of a Pull Request by running benchmarks on +the CI, check out [How to: Running core benchmarks on Node.js CI][benchmark-ci]. + +## Creating a benchmark + +### Basics of a benchmark + +All benchmarks use the `require('../common.js')` module. This contains the +`createBenchmark(main, configs[, options])` method which will setup the +benchmark. + +The arguments of `createBenchmark` are: + +* `main` {Function} The benchmark function, + where the code running operations and controlling timers should go +* `configs` {Object} The benchmark parameters. `createBenchmark` will run all + possible combinations of these parameters, unless specified otherwise. + Each configuration is a property with an array of possible values. + The configuration values can only be strings or numbers. +* `options` {Object} The benchmark options. At the moment only the `flags` + option for specifying command line flags is supported. + +`createBenchmark` returns a `bench` object, which is used for timing +the runtime of the benchmark. Run `bench.start()` after the initialization +and `bench.end(n)` when the benchmark is done. `n` is the number of operations +performed in the benchmark. + +The benchmark script will be run twice: + +The first pass will configure the benchmark with the combination of +parameters specified in `configs`, and WILL NOT run the `main` function. +In this pass, no flags except the ones directly passed via commands +when running the benchmarks will be used. + +In the second pass, the `main` function will be run, and the process +will be launched with: + +* The flags passed into `createBenchmark` (the third argument) +* The flags in the command passed when the benchmark was run + +Beware that any code outside the `main` function will be run twice +in different processes. This could be troublesome if the code +outside the `main` function has side effects. In general, prefer putting +the code inside the `main` function if it's more than just declaration. + +```js +'use strict'; +const common = require('../common.js'); +const { SlowBuffer } = require('buffer'); + +const configs = { + // Number of operations, specified here so they show up in the report. + // Most benchmarks just use one value for all runs. + n: [1024], + type: ['fast', 'slow'], // Custom configurations + size: [16, 128, 1024] // Custom configurations +}; + +const options = { + // Add --expose-internals in order to require internal modules in main + flags: ['--zero-fill-buffers'] +}; + +// `main` and `configs` are required, `options` is optional. +const bench = common.createBenchmark(main, configs, options); + +// Any code outside main will be run twice, +// in different processes, with different command line arguments. + +function main(conf) { + // Only flags that have been passed to createBenchmark + // earlier when main is run will be in effect. + // In order to benchmark the internal modules, require them here. For example: + // const URL = require('internal/url').URL + + // Start the timer + bench.start(); + + // Do operations here + const BufferConstructor = conf.type === 'fast' ? Buffer : SlowBuffer; + + for (let i = 0; i < conf.n; i++) { + new BufferConstructor(conf.size); + } + + // End the timer, pass in the number of operations + bench.end(conf.n); +} +``` + +### Creating an HTTP benchmark + +The `bench` object returned by `createBenchmark` implements +`http(options, callback)` method. It can be used to run external tool to +benchmark HTTP servers. + +```js +'use strict'; + +const common = require('../common.js'); + +const bench = common.createBenchmark(main, { + kb: [64, 128, 256, 1024], + connections: [100, 500] +}); + +function main(conf) { + const http = require('http'); + const len = conf.kb * 1024; + const chunk = Buffer.alloc(len, 'x'); + const server = http.createServer((req, res) => { + res.end(chunk); + }); + + server.listen(common.PORT, () => { + bench.http({ + connections: conf.connections, + }, () => { + server.close(); + }); + }); +} +``` + +Supported options keys are: + +* `port` - defaults to `common.PORT` +* `path` - defaults to `/` +* `connections` - number of concurrent connections to use, defaults to 100 +* `duration` - duration of the benchmark in seconds, defaults to 10 +* `benchmarker` - benchmarker to use, defaults to +`common.default_http_benchmarker` + +[autocannon]: https://github.com/mcollina/autocannon +[wrk]: https://github.com/wg/wrk +[t-test]: https://en.wikipedia.org/wiki/Student%27s_t-test#Equal_or_unequal_sample_sizes.2C_unequal_variances +[git-for-windows]: https://git-scm.com/download/win +[nghttp2.org]: https://nghttp2.org +[benchmark-ci]: https://github.com/nodejs/benchmarking/blob/master/docs/core_benchmarks.md |