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Sandmark is a suite of OCaml benchmarks and a collection of tools to configure different compiler variants, run and visualise the results. Sandmark includes both sequential and parallel benchmarks. The results from the nightly benchmark runs are available at

Quick Start

On Ubuntu 18.04.4 LTS you can try the following commands:

$ sudo apt-get install curl git libgmp-dev libdw-dev python3-pip jq jo bubblewrap \
    pkg-config m4 unzip
$ pip3 install jupyter seaborn pandas intervaltree

# Install OPAM if not available already
$ sh <(curl -sL
$ opam init

$ git clone
$ cd sandmark

## For 4.14.0+domains

$ make ocaml-versions/4.14.0+domains.bench

## For 5.1.0+trunk

$ opam pin add -n --yes dune 3.5.0
$ opam install dune

$ TAG='"run_in_ci"' make run_config_filtered.json
$ USE_SYS_DUNE_HACK=1 RUN_CONFIG_JSON=run_config_filtered.json make ocaml-versions/5.1.0+trunk.bench

You can now find the results in the _results/ folder.


On GNU/Linux you need to have libgmp-dev installed for several of the benchmarks to work. You also need to have libdw-dev installed for the profiling functionality of orun to work on Linux.

You can run make depend that will check for any missing dependencies.


Sandmark uses opam, with a static local repository, to build external libraries and applications. It then builds any sandmark OCaml benchmarks and any data dependencies. Following this it runs the benchmarks as defined in the run_config.json

These stages are implemented in:

  • Opam setup: the Makefile handles the creation of an opam switch that builds a custom compiler as specified in the ocaml-versions/<version>.var file. It then installs all the required packages; these packages are statically defined by their opam files in the dependencies directory.

  • Runplan: the list of benchmarks which will run along with the measurement wrapper (e.g. orun or perf) is specified in run_config.json. This config file is used to generate dune files which will run the benchmarks.

  • Build: dune is used to build all the sandmark OCaml benchmarks that are in the benchmarks directory.

  • Execute: dune is used to execute all the benchmarks sepcified in the runplan using the benchmark wrapper defined in run_config.json and specified via the RUN_BENCH_TARGET variable passed to the makefile.

Configuration of the compiler build

The compiler variant and its configuration options can be specified in a .json file in the ocaml-versions/ directory. It uses the JSON syntax as shown in the following example:

  "url" : "",
  "configure" : "-q",
  "runparams" : "v=0x400"

The various options are described below:

  • url is MANDATORY and provides the web URL to download the source for the ocaml-base-compiler.

  • configure is OPTIONAL, and you can use this setting to pass specific flags to the configure script.

  • runparams is OPTIONAL, and its values are passed to OCAMLRUNPARAM when building the compiler. Note that this variable is not used for the running of benchmarks, just the build of the compiler



The orun wrapper is packaged in orun/, it collects runtime and OCaml garbage collector statistics producing output in a JSON format. You can use orun independently of the sandmark benchmarking suite, by installing it as an opam pin (e.g. opam install . from within orun/).

Using a directory different than /home

Special care is needed if you happen to run sandmark from a directory different than home.

If you get error like # bwrap: execvp dune: No such file or directory, it may be because opam's sandboxing prevent executables to be run from non-standard locations.

In order to get around this issue, you may specify OPAM_USER_PATH_RO=/directory/to/sandmark in order to whitelist this location from sandboxing.


You can execute both serial and parallel benchmarks using the and scripts. Ensure that the respective .json configuration files have the appropriate settings.

If using RUN_BENCH_TARGET=run_orunchrt then the benchmarks will run using chrt -r 1.

IMPORTANT: chrt -r 1 is necessary when using taskset to run parallel programs. Otherwise, all the domains will be scheduled on the same core and you will see slowdown with increasing number of domains.

You may need to give the user permissions to execute chrt, one way to do this can be:

sudo setcap cap_sys_nice=ep /usr/bin/chrt

Configuring the benchmark runs

A config file can be specified with the environment variable RUN_CONFIG_JSON, and the default value is run_config.json. This file lists the executable to run and the wrapper which will be used to collect data (e.g. orun or perf). You can edit this file to change benchmark parameters or wrappers.

The environment within which a wrapper runs allows the user to configure variables such as OCAMLRUNPARAM or LD_PRELOAD. For example this wrapper configuration:

  "name": "orun-2M",
  "environment": "OCAMLRUNPARAM='s=2M'",
  "command": "orun -o %{output} -- taskset --cpu-list 5 %{command}"

would allow

$ RUN_BENCH_TARGET=run_orun-2M make ocaml-versions/5.0.0+trunk.bench

to run the benchmarks on 5.0.0+trunk with a 2M minor heap setting taskset onto CPU 5.


The benchmarks also have associated tags which classify the benchmarks. The current tags are:

  • macro_bench - A macro benchmark. Benchmarks with this tag are automatically run nightly.
  • run_in_ci - This benchmark is run in the CI.
  • lt_1s - running time is less than 1s on the turing machine.
  • 1s_10s - running time is between 1s and 10s on the turing machine.
  • 10s_100s - running time is between 10s and 100s on the turing machine.
  • gt_100s - running time is greater than 100s on the turing machine.

The benchmarking machine turing is an Intel Xeon Gold 5120 CPU with 64GB of RAM housed at IITM.

The run_config.json file may be filtered based on the tag. For example,

$ TAG='"macro_bench"' make run_config_filtered.json

filters the run_config.json file to only contain the benchmarks tagged as macro_bench.

Running benchmarks

The build bench target determines the type of benchmark being built. It can be specified with the environment variable BUILD_BENCH_TARGET, and the default value is buildbench which runs the serial benchmarks. For executing the parallel benchmarks use multibench_parallel. You can also setup a custom bench and add only the benchmarks you care about.

Sandmark has support to build and execute the serial benchmarks in byte mode. A separate run_config_byte.json file has been created for the same. These benchmarks are relatively slower compared to their native execution. You can use the following commands to run the serial benchmarks in byte mode:

$ opam install dune.2.9.0
    RUN_CONFIG_JSON=run_config_byte.json make ocaml-versions/5.0.0+stable.bench

We can obtain throughput and latency results for the benchmarks. To obtain latency results, we can set the environment variable RUN_BENCH_TARGET to run_pausetimes, which will run the benchmarks with olly and collect the GC tail latency profile of the runs (see the script pausetimes/pausetimes). The results will be files in the _results directory with a .pausetimes.*.bench suffix.

The perf stat output results can be obtained by setting the environment variable RUN_BENCH_TARGET to run_perfstat. In order to use the perf command, the kernel.perf_event_paranoid parameter should be set to -1 using the sysctl command. For example:

$ sudo sysctl -w kernel.perf_event_paranoid=-1

You can also set it permanently in the /etc/sysctl.conf file.


After a run is complete, the results will be available in the _results directory.

Jupyter notebooks are available in the notebooks directory to parse and visualise the results, for both serial and parallel benchmarks. To run the Jupyter notebooks for your results, copy your results to notebooks/ sequential folder for sequential benchmarks and notebooks/parallel folder for parallel benchmarks. It is sufficient to copy only the consolidated bench files, which are present as _results/<comp-version>/<comp-version>.bench. You can run the notebooks with

$ jupyter notebook


The logs for nightly runs are available at here. Runs which are considered successful are copied to the main branch of the repo, so that they can be visualized using the sandmark nightly UI

Adding benchmarks

You can add new benchmarks as follows:

  • Add dependencies to packages: If there are any package dependencies your benchmark has that are not already included in Sandmark, add its opam file to dependencies/packages/<package-name>/<package-version>/opam. If the package depends on other packages, repeat this step for all of those packages. Add the package to PACKAGES variable in the Makefile.

  • Add benchmark files: Find a relevant folder in benchmarks/ and add your code to it. Feel free to create a new folder if you don't find any existing ones relevant. Every folder in benchmarks/ has its own dune file; if you are creating a new directory for your benchmark, also create a dune file in that directory and add a stanza for your benchmark. If you are adding your benchmark to an existing directory, add a dune stanza for your benchmark in the directory's dune file.

    Also add you code and input files if any to an alias, buildbench for sequential benchmarks and multibench_parallel for parallel benchmarks. For instance, if you are adding a parallel benchmark and its input file input.txt to a directory, in that directory's dune file add

    (alias (name multibench_parallel) (deps input.txt))
  • Add commands to run your applications: Add an entry for your benchmark run to the appropriate config file; run_config.json for sequential benchmarks and multicore_parallel_run_config.json for parallel benchmarks.

    If you want the benchmark to be run nightly, make sure it has the macro_bench tag. Additionally if you want to be able to correctly visualize the results of the benchmark, it should follow a few conventions:

    1. Its name should be foo for the serial version and foo_multicore for the parallel version (a parallel version running on a single core is still _multicore)
    2. The first argument in params should be the number of domains, followed possibly by other parameters. If that is not feasible, add a short_name field with the format <num_domains>_<other_arg> with an _ separating the number of domains and other arguments.

Config files

The *_config.json files used to build benchmarks

  • run_config.json : Runs sequential benchmarks with stock OCaml variants in CI and sandmark-nightly on the IITM machine(turing)
  • multicore_parallel_run_config.json : Runs parallel benchmarks with multicore OCaml in CI and sandmark-nightly on the IITM machine(turing)
  • multicore_parallel_navajo_run_config.json : Runs parallel benchmarks with multicore OCaml in sandmark-nightly on Navajo (AMD EPYC 7551 32-Core Processor) machine
  • micro_multicore.json : To locally run multicore specific micro benchmarks

Benchmarks status

The following table marks the benchmarks that are currently not working with any one of the variants that are used in the CI. These benchmarks are known to fail and have an issue tracking their progress.

Variants Benchmarks Issue Tracker
5.0.0+trunk.bench irmin benchmarks sandmark#262
4.14.0+domains.bench irmin benchmarks sandmark#262


JupyterHub is a multi-user server for hosting Jupyter notebooks. The Littlest JupyterHub (TLJH) installation is capable of hosting 0-100 users.

The following steps can be used for installation on Ubuntu 18.04.4 LTS:

$ sudo apt install python3 python3-dev git curl
$ curl | \
  sudo -E python3 - --admin adminuser

If you would like to run the the service on a specific port, say "8082", you need to update the same in /opt/tljh/state/traefix.toml file.

You can verify that the services are running from:

$ sudo systemctl status traefik
$ sudo systemctl status jupyterhub

By default, the hub login opens at hostname:15001/hub/login, which is used by the admin user to create user accounts. The users will be able to login using hostname:8082/user/username/tree.

You can also setup HTTPS using Let's Encrypt with JuptyerHub using the following steps:

$ sudo tljh-config set https.enabled true
$ sudo tljh-config set e-mail
$ sudo tljh-config add-item example.domain
$ sudo tljh-config show
$ sudo tljh-config reload proxy


Multicore Notes


ctypes 14.0.0 doesn't support multicore yet. A workaround is to update dependencies/packages/ctypes/ctypes.0.14.0/opam to use as the source url.


This is only needed for multicore versions before this commit

The ocaml-update-c command in multicore needs to run with GNU sed. sed will default to a BSD sed on OS X. One way to make things work on OS X is to install GNU sed with homebrew and then update the PATH you run sandmark with to pick up the GNU version.

Makefile Variables

Name Description Default Values Usage
BENCH_COMMAND TAG selection and make command to run benchmarks 4.14.0+domains for CI With current-bench
BUILD_BENCH_TARGET Target selection for sequential (buildbench) and parallel (multibench) benchmarks buildbench building benchmark
BUILD_ONLY If the value is equal to 0 then execute the benchmarks otherwise skip the benchmark execution and exit the sandmark build process 0 building benchmark
CONTINUE_ON_OPAM_INSTALL_ERROR Allow benchmarks to continue even if the opam package install errors out true executing benchmark
DEPENDENCIES List of Ubuntu dependencies libgmp-dev libdw-dev jq python3-pip pkg-config m4 building compiler and its dependencies
ENVIRONMENT Function that gets the environment parameter from wrappers in *_config.json null string building compiler and its dependencies
ITER Indicates the number of iterations the sandmark benchmarks would be executed 1 executing benchmark
OCAML_CONFIG_OPTION Function that gets the runtime parameters configure in ocaml-versions/*.json null string building compiler and its dependencies
OCAML_RUN_PARAM Function that gets the runtime parameters run_param in ocaml-versions/*.json null string building compiler and its dependencies
PACKAGES List of all the benchmark dependencies in sandmark cpdf conf-pkg-config conf-zlib bigstringaf decompress camlzip menhirLib menhir minilight base stdio dune-private-libs dune-configurator camlimages yojson lwt zarith integers uuidm react ocplib-endian nbcodec checkseum sexplib0 eventlog-tools irmin cubicle conf-findutils index logs mtime ppx_deriving ppx_deriving_yojson ppx_irmin repr ppx_repr irmin-layers irmin-pack building benchmark
PIP_DEPENDENCIES List of Python dependencies intervaltree building compiler and its dependencies
PRE_BENCH_EXEC Any specific commands that needed to be executed before the benchmark. For eg. PRE_BENCH_EXEC='taskset --cpu-list 3 setarch uname -m --addr-no-randomize' null string executing benchmark
RUN_BENCH_TARGET The executable to be used to run the benchmarks run_orun executing benchmark
RUN_CONFIG_JSON Input file selection that contains the list of benchmarks run_config.json executing benchmark
SANDMARK_DUNE_VERSION Default dune version to be used 2.9.0 building compiler and its dependencies
SANDMARK_OVERRIDE_PACKAGES A list of dependency packages with versions that can be overrided (optional) "" building compiler and its dependencies
SANDMARK_REMOVE_PACKAGES A list of dependency packages to be dynamically removed (optional) "" building compiler and its dependencies
SANDMARK_URL OCaml compiler source code URL used to build the benchmarks "" building compiler and its dependencies
SYS_DUNE_BASE_DIR Function that returns the path of the system installed dune for use with benchmarking dune package present in the local opam switch building compiler and its dependencies
USE_SYS_DUNE_HACK If the value is 1 then use system installed dune 0 building compiler and its dependencies
WRAPPER Function to get the wrapper out of run_<wrapper-name> run_orun executing benchmark