ruby-bench

Small set of benchmarks and scripts for the Ruby programming language.

The benchmarks are found in the benchmarks directory. Individual Ruby files in benchmarks are microbenchmarks. Subdirectories under benchmarks are larger macrobenchmarks. Each benchmark relies on a harness found in ./harness/harness.rb. The harness controls the number of times a benchmark is run, and writes timing values into an output file.

The run_benchmarks.rb script (optional) traverses the benchmarks directory and runs the benchmarks in there. It reads the output file written by the benchmarking harness. The output is written to multiple files at the end -- CSV, text and JSON -- so that results can be easily viewed or graphed in any spreadsheet editor.

Installation

Clone this repository:

git clone https://github.com/ruby/ruby-bench

Benchmarking YJIT

ruby-bench supports benchmarking any Ruby implementation. But if you want to benchmark YJIT, follow these instructions to build and install YJIT.

If you install it with the name ruby-yjit on chruby, you should enable it before running ./run_benchmarks.rb:

chruby ruby-yjit

Usage

To run all the benchmarks and record the data:

cd ruby-bench
./run_benchmarks.rb

This runs for a few minutes and produces a table like this in the console (results below not up to date):

-------------  -----------  ----------  ---------  ----------  -----------  ------------
bench          interp (ms)  stddev (%)  yjit (ms)  stddev (%)  interp/yjit  yjit 1st itr
30k_ifelse     2372.0       0.0         447.6      0.1         5.30         4.16
30k_methods    6328.3       0.0         963.4      0.0         6.57         6.25
activerecord   171.7        0.8         144.2      0.7         1.19         1.15
binarytrees    445.8        2.1         389.5      2.5         1.14         1.14
cfunc_itself   105.7        0.2         58.7       0.7         1.80         1.80
fannkuchredux  6697.3       0.1         6714.4     0.1         1.00         1.00
fib            245.3        0.1         77.1       0.4         3.18         3.19
getivar        97.3         0.9         44.3       0.6         2.19         0.98
lee            1269.7       0.9         1172.9     1.0         1.08         1.08
liquid-render  204.5        1.0         172.4      1.3         1.19         1.18
nbody          121.9        0.1         121.6      0.3         1.00         1.00
optcarrot      6260.2       0.5         4723.1     0.3         1.33         1.33
railsbench     3827.9       0.9         3581.3     1.3         1.07         1.05
respond_to     259.0        0.6         197.1      0.4         1.31         1.31
setivar        73.1         0.2         53.3       0.7         1.37         1.00
-------------  -----------  ----------  ---------  ----------  -----------  ------------

The interp/yjit column is the ratio of the average time taken by the interpreter over the average time taken by YJIT after a number of warmup iterations. Results above 1 represent speedups. For instance, 1.14 means "YJIT is 1.14 times as fast as the interpreter".

Specific categories

By default, run_benchmarks.rb runs all three benchmark categories, --category headline,other,micro. You can run only benchmarks with specific categories:

./run_benchmarks.rb --category micro

You can also only the headline benchmarks with the --headline option:

./run_benchmarks.rb --headline

Specific benchmarks

To run one or more specific benchmarks and record the data:

./run_benchmarks.rb fib lee optcarrot

Running a single benchmark

This is the easiest way to run a single benchmark. It requires no setup at all and assumes nothing about the Ruby you are benchmarking. It's also convenient for profiling, debugging, etc, especially since all benchmarked code runs in that process.

ruby benchmarks/some_benchmark.rb

Benchmark organization

Benchmarks can be organized in three ways:

Standalone .rb files - Place a .rb file directly in the benchmarks/ directory:
```
benchmarks/fib.rb         # Benchmark name: "fib"
```
Single benchmark per directory - For benchmarks that need additional files (like Gemfiles):
```
benchmarks/erubi/
  benchmark.rb            # Benchmark name: "erubi"
  Gemfile
```
Multiple benchmarks per directory - For related benchmarks sharing dependencies:
```
benchmarks/addressable/
  equality.rb             # Benchmark name: "addressable-equality"
  join.rb                 # Benchmark name: "addressable-join"
  Gemfile                 # Shared Gemfile
```
In directories without a benchmark.rb file, all .rb files will be discovered as separate benchmarks. The benchmark name is derived as directoryname-suffix from suffix.rb files.

Ractor Benchmarks

ruby-bench supports Ractor-specific benchmarking with dedicated categories and benchmark directories.

Ractor Categories

There are two Ractor-related categories:

--category ractor - Runs both regular benchmarks marked with ractor: true in benchmarks.yml AND all benchmarks from the benchmarks-ractor directory. The harness-ractor harness is used for both types of benchmark.
--category ractor-only - Runs ONLY benchmarks from the benchmarks-ractor directory, ignoring regular benchmarks even if they are marked with ractor: true. This category also automatically uses the harness-ractor harness.

Directory Structure

The benchmarks-ractor/ directory sits at the same level as the main benchmarks directory, and contains Ractor-specific benchmark implementations that are designed to test Ractor functionality. They are not intended to be used with any harness except harness-ractor.

Usage Examples

# Run all Ractor-capable benchmarks (both regular and Ractor-specific)
./run_benchmarks.rb --category ractor

# Run only dedicated Ractor benchmarks from benchmarks-ractor directory
./run_benchmarks.rb --category ractor-only

Note: The harness-ractor harness is automatically selected when using these categories, so there's no need to specify --harness manually.

Ractor counts

The Ractor harness measures each benchmark at 0 (the main Ractor only), 1, 2, 4, 6, and 8 Ractors. Set RUBY_BENCH_RACTORS to a comma-separated list to change the counts, for example RUBY_BENCH_RACTORS=0,2,8.

run_benchmarks.rb starts a fresh process for each count. Heap pages, the GC page pool, and JIT state therefore cannot carry over from one count to the next. Each process runs WARMUP_ITRS warmup iterations at its own count before the measured iterations. As in the default harness, the harness prints each warmup iteration and records its time.

The JSON output keeps one blob per benchmark. warmup_by_ractors, bench_by_ractors, and gc_by_ractors hold the measurements for each count. warmup_by_ractors holds wall times only. The --ractor-gc mode does not keep GC samples for warmup iterations. results_by_ractors holds the process-level data of each count: rss, maxrss, YJIT or ZJIT stats, and command_line. The blob has no top-level rss, maxrss, or JIT stats, because no single process ran all counts.

The text summary, the CSV output, and misc/zjit_diff.rb show one row for each count, with the RSS and JIT stats of that count's process.

When you run a benchmark directly with -Iharness-ractor, the harness runs all counts in one process, one count after another.

Ractor Scenario Benchmarks

By default, harness-ractor spawns the worker Ractors and runs the benchmark block inside each of them. A benchmark that calls run_benchmark(n, scenario: true) uses scenario mode instead. The harness calls the block one time per trial in the main Ractor, with the Ractor count as its argument. The block spawns and coordinates its own Ractors. When the block returns a proc, the harness calls the proc after the retention measurement.

Scenario mode skips Ractor count 0 and runs no warmup. For each trial, the harness records:

the time of the block call, which includes all work in the block;
the retained RSS: the RSS after a full GC, minus the RSS of the process before the first trial;
the peak RSS: the highest RSS that the harness reads just before the block call, every 5 ms during it (RACTOR_MEM_PEAK_SAMPLE_INTERVAL), and just after it.

run_benchmarks.rb runs a scenario benchmark in one process per count, like other Ractor benchmarks. It starts no count-0 process when the benchmark's benchmarks.yml entry sets ractor_scenario: true; without that key, the count-0 process fails. Each process measures retained RSS against its own base RSS, so the JSON output keeps ractor_mem_base_rss in results_by_ractors.

Three benchmarks use scenario mode to measure pathological memory behaviour with multiple ractors, for GC work that reclaims ractor-local memory:

ractor-dead-set - Every ractor builds a large live set and terminates. Retention shows how much of the dead ractors' final live sets a full GC leaves resident.
ractor-idle-garbage - Every ractor builds a large set, drops all references, then idles without allocating. The garbage cannot be swept while the ractor idles.
ractor-msg-backlog - Unshareable payloads flood the queues of gated consumer ractors, duplicating the payload data per consumer. Its time includes the gate sleep (RACTOR_BACKLOG_GATE_SLEEP, default 1 second).

# Every count in one process
ruby -Iharness-ractor benchmarks/ractor-dead-set/benchmark.rb

# One process per count, comparing two Rubies, with Ractor GC metrics
RUBY_BENCH_RACTORS=1,2,4,6,8 ./run_benchmarks.rb --category ractor --ractor-gc \
  --chruby "base::ruby-base --yjit" --chruby "exp::ruby-exp --yjit" ractor-dead-set

The harness prints BENCH_METRIC retained_mib=<worst count median> and BENCH_METRIC peak_mib=... lines, plus one pair per ractor count. The JSON fields ractor_mem_medians and ractor_mem_samples hold the same data; each ractor_mem_medians entry also carries <metric>_mean and <metric>_max over the same trials. run_benchmarks.rb prints a Scenario memory table, one row per ractor count, below the GC tables of the section: retained med and retained mean for retention, and peak, the highest peak any trial reached. The ractor counts and trials are controlled with RUBY_BENCH_RACTORS (default 1,2,4,6,8) and MIN_BENCH_ITRS (default 3 for these benchmarks).

The harness collects with GC.start(global: true) when the target Ruby's GC.start accepts the global: keyword. Some Ruby 4.1 builds do not accept it. On a target with Ractor-local GC, a plain GC.start collects only the main Ractor's object space. The JSON field ractor_mem_settle records global or default.

After collecting, the harness calls glibc's malloc_trim(0) so that memory Ruby has freed is returned to the OS rather than counted as retained. Where libc has no malloc_trim (macOS, musl), it prints why and skips the trim. The JSON field ractor_mem_malloc_trim records whether libc has malloc_trim.

Set RUBY_BENCH_PROFILING=1 to skip these collections, the trim and the settle sleep, so a profile of a scenario benchmark shows only the scenario. The retained RSS then includes uncollected garbage.

With --ractor-gc (RUBY_BENCH_RACTOR_GC=1), the harness cannot see which Ractors are workers. A scenario wraps each worker body in measure_worker_gc { ... }, which returns [result, sample]. The main Ractor passes each sample to record_worker_gc(worker_index, sample). A trial fails when its recorded worker indexes are not 0...count.

Worker samples cover only the workers' own object spaces during the scenario. They do not include allocation by the main Ractor, such as the payloads that ractor-msg-backlog sends. They also do not include the GCs that the harness runs to measure retention. The JSON field gc_controller_samples covers the main Ractor during the scenario.

Ruby options

By default, ruby-bench benchmarks the Ruby used for run_benchmarks.rb. If the Ruby has --yjit option, it compares two Ruby commands, -e "interp::ruby" and -e "yjit::ruby --yjit. However, if you specify -e yourself, you can override what Ruby is benchmarked.

# "xxx::" prefix can be used to specify a shorter name/alias, but it's optional.
./run_benchmarks.rb -e "ruby" -e "yjit::ruby --yjit"

# You could also measure only a single Ruby
./run_benchmarks.rb -e "3.1.0::/opt/rubies/3.1.0/bin/ruby"

# With --chruby, you can easily specify rubies managed by chruby
./run_benchmarks.rb --chruby "3.1.0" --chruby "3.1.0+YJIT::3.1.0 --yjit"

# ";" can be used to specify multiple executables in a single option
./run_benchmarks.rb --chruby "3.1.0;3.1.0+YJIT::3.1.0 --yjit"

YJIT options

You can use --yjit_opts to specify YJIT command-line options:

./run_benchmarks.rb --yjit_opts="--yjit-version-limit=10" fib lee optcarrot

Running pre-init code

It is possible to use run_benchmarks.rb to run arbitrary code before each benchmark run using the --with-pre-init option.

For example: to run benchmarks with GC.auto_compact enabled a pre-init.rb file can be created, containing GC.auto_compact=true, and this can be passed into the benchmarks in the following way:

./run_benchmarks.rb --with-pre-init=./pre-init.rb

This file will then be passed to the underlying Ruby interpreter with -r.

Harnesses

You can find several test harnesses in this repository:

harness - the normal default harness, with duration controlled by warmup iterations and time/count limits
harness-bips - a harness that measures iterations/second until stable
harness-continuous - a harness that adjusts the batch sizes of iterations to run in stable iteration size batches
harness-once - a simplified harness that simply runs once
harness-perf - a simplified harness that runs for exactly the hinted number of iterations
harness-stackprof - a harness to profile the benchmark with stackprof
harness-stats - count method calls and loop iterations
harness-vernier - a harness to profile the benchmark with vernier
harness-warmup - a harness which runs as long as needed to find warmed up (peak) performance

To use it, run a benchmark script directly, specifying a harness directory with -I:

ruby -Iharness benchmarks/railsbench/benchmark.rb

There is also a robust but complex CI harness in the yjit-metrics repo.

Iterations and duration

With the default harness, the number of iterations and duration can be controlled by the following environment variables:

WARMUP_ITRS: The number of warm-up iterations, ignored in the final comparison (default: 15)
MIN_BENCH_ITRS: The minimum number of benchmark iterations (default: 10)
MIN_BENCH_TIME: The minimum seconds for benchmark (default: 10)

You can also use --warmup, --bench, or --once to set these environment variables:

# same as: WARMUP_ITRS=2 MIN_BENCH_ITRS=3 MIN_BENCH_TIME=0 ./run_benchmarks.rb railsbench
./run_benchmarks.rb railsbench --warmup=2 --bench=3

# same as: WARMUP_ITRS=0 MIN_BENCH_ITRS=1 MIN_BENCH_TIME=0 ./run_benchmarks.rb railsbench
./run_benchmarks.rb railsbench --once

There is also a handy script for running benchmarks just once using WARMUP_ITRS=0 MIN_BENCH_ITRS=1 MIN_BENCH_TIME=0, for example with the --yjit-stats command-line option:

./run_once.sh --yjit-stats benchmarks/railsbench/benchmark.rb

Using perf

There is also a harness to use Linux perf. By default, it only runs a fixed number of iterations. If PERF environment variable is present, it starts the perf subcommand after warmup.

# Use `perf record` for both warmup and benchmark
perf record ruby --yjit-perf=map -Iharness-perf benchmarks/railsbench/benchmark.rb

# Use `perf record` only for benchmark
PERF=record ruby --yjit-perf=map -Iharness-perf benchmarks/railsbench/benchmark.rb

This is the only harness that uses run_benchmark's argument, num_itrs_hint.

Using samply

samply is a sampling profiler for macOS and Linux that shows its profiles in the Firefox Profiler. Run the benchmark script directly under samply record:

samply record ruby -Iharness benchmarks/railsbench/benchmark.rb

# Name JIT-compiled methods. Both JITs write /tmp/perf-<pid>.map, which samply reads.
samply record ruby --yjit --yjit-perf -Iharness benchmarks/railsbench/benchmark.rb
samply record ruby --zjit --zjit-perf -Iharness benchmarks/railsbench/benchmark.rb

# Save the profile without opening it, and open it later
samply record --save-only -o railsbench.json.gz ruby -Iharness benchmarks/railsbench/benchmark.rb
samply load railsbench.json.gz

The profile includes warmup. Use WARMUP_ITRS, MIN_BENCH_ITRS and MIN_BENCH_TIME (see Iterations and duration) to change how long each phase runs, or select the measured iterations in the profiler's timeline.

A direct run of a Ractor benchmark runs every Ractor count in one process, so set RUBY_BENCH_RACTORS to the one count you want to profile. For a scenario benchmark, also set RUBY_BENCH_PROFILING=1 to keep the harness's retention GCs out of the profile. The worker Ractors show up as separate thread tracks.

RUBY_BENCH_RACTORS=4 RUBY_BENCH_PROFILING=1 samply record ruby -Iharness-ractor benchmarks/ractor-dead-set/benchmark.rb

samply also records child processes, so samply record ruby run_benchmarks.rb ... profiles every benchmark process, next to the setup commands of run_benchmarks.rb itself.

On macOS, samply cannot profile Apple-signed binaries. Use ruby run_benchmarks.rb, not ./run_benchmarks.rb, which starts through /usr/bin/env. A Ruby you built or installed with a version manager is fine.
On Linux, samply needs access to perf events, for example sudo sysctl kernel.perf_event_paranoid=1.

Printing YJIT stats

The --yjit-stats option of ./run_benchmarks.rb allows you to print the diff of YJIT stats counters after each iteration with the default harness.

./run_benchmarks.rb --yjit-stats=code_region_size,yjit_alloc_size

Measuring memory usage

--rss option of run_benchmarks.rb allows you to measure RSS (resident set size).

./run_benchmarks.rb --rss

The harness samples RSS once per iteration across the benchmarking window (after warmup), so the RSS (MiB) column reports the mean working set during measurement along with its run-to-run variability (mean ± stddev%), and the RSS ratio is computed from those means. The raw per-iteration samples are stored in the JSON output under rss_samples (bytes).

For reference, the JSON output also keeps rss, a single snapshot taken after a full GC at the end of the run (the retained set, a lower bound), and maxrss, the process's lifetime peak from getrusage.

Measuring Ractor GC activity

The --ractor-gc option of run_benchmarks.rb collects Ractor-local GC metrics for benchmarks that use the Ractor harness (--category ractor), in both the per-worker mode and scenario mode. The target must use Ruby 4.1 or newer with per-Ractor global GC attribution (ruby/ruby#19147); older targets fail before warmup.

./run_benchmarks.rb --category ractor --chruby=base::ruby-base --ractor-gc

# One benchmark, run directly. --ractor-gc sets RUBY_BENCH_RACTOR_GC=1.
RUBY_BENCH_RACTOR_GC=1 ruby -Iharness-ractor benchmarks/ractor-dead-set/benchmark.rb

run_benchmarks.rb only runs Ractor harness benchmarks with --category ractor or --category ractor-only. Without one, it skips them even when you name them. Ractor Scenario Benchmarks has an example that compares two Rubies on one benchmark.

Each measured iteration samples GC.stat and GC total time in every worker Ractor's own object space. The JSON output records the scope as gc_scope: "ractor-local-workload", gc_stat_scope: "ractor-local", and gc_measure_total_time_scope: "ractor-local", plus the target's gc_config.

The text summary shows GC data in separate tables after the timing table. A single-executable report has one GC summary table. A comparison report has a GC time ratios table (base/comparison) and a GC counts table (base → comparison). A table hides a column that has no data in any row and lists the hidden columns below the table. A ratio column has no data when it is N/A in every row; a 0.000 ratio stays visible. Any other column has no data when it is zero or N/A in every row.

Tables marked worker sum add the Ractor-local counters and GC times of the sampled workers of each iteration. GCs/iter is the sum of minor/iter, major/iter, and global/iter; a global cycle counts under global on the Ractor that initiated it, not under major. Single-executable reports also show GC ms/worker, which divides each iteration's worker-sum GC time by its sampled worker count, then averages.
compacts* shows the main Ractor's GC.stat(:compact_count) delta. Every global compacting cycle increments it in every object space, so it is not summed across workers.

Worker records in the JSON output never contain the controller-observed counter, and it is never summed across workers.

Rendering a graph

--graph option of run_benchmarks.rb allows you to render benchmark results as a graph.

# Write a graph at data/output_XXX.png (it will print the path)
./run_benchmarks.rb --graph

Installation

Before using this option, you might need to install the dependencies of Gruff:

# macOS
brew install imagemagick

# Ubuntu
sudo apt-get install libmagickwand-dev

Changing font size

You can regenerate a graph with misc/graph.rb, changing its font size.

Usage: misc/graph.rb [options] CSV_PATH
        --title SIZE                 title font size
        --legend SIZE                legend font size
        --marker SIZE                marker font size

Disabling CPU Frequency Scaling

To disable CPU frequency scaling with an Intel CPU, edit /etc/default/grub or /etc/default/grub.d/50-cloudimg-settings.cfg and add intel_pstate=no_hwp to GRUB_CMDLINE_LINUX_DEFAULT. It’s a space-separated list.

Then:

sudo update-grub
sudo reboot
sudo sh -c 'echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo'

To verify things worked:

cat /proc/cmdline to see the intel_pstate=no_hwp parameter is in there
ls /sys/devices/system/cpu/intel_pstate/ and hwp_dynamic_boost should not exist
cat /sys/devices/system/cpu/intel_pstate/no_turbo should say 1

Helpful docs:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/processor_state_control.html#baseline-perf

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ruby-bench

Installation

Benchmarking YJIT

Usage

Specific categories

Specific benchmarks

Running a single benchmark

Benchmark organization

Ractor Benchmarks

Ractor Categories

Directory Structure

Usage Examples

Ractor counts

Ractor Scenario Benchmarks

Ruby options

YJIT options

Running pre-init code

Harnesses

Iterations and duration

Using perf

Using samply

Printing YJIT stats

Measuring memory usage

Measuring Ractor GC activity

Rendering a graph

Installation

Changing font size

Disabling CPU Frequency Scaling

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ruby-bench

Installation

Benchmarking YJIT

Usage

Specific categories

Specific benchmarks

Running a single benchmark

Benchmark organization

Ractor Benchmarks

Ractor Categories

Directory Structure

Usage Examples

Ractor counts

Ractor Scenario Benchmarks

Ruby options

YJIT options

Running pre-init code

Harnesses

Iterations and duration

Using perf

Using samply

Printing YJIT stats

Measuring memory usage

Measuring Ractor GC activity

Rendering a graph

Installation

Changing font size

Disabling CPU Frequency Scaling