Defining Custom Workloads

Workloads in FireSim consist of a series of Jobs that are assigned to be run on individual simulations. Currently, we require that a Workload defines either:

  • A single type of job, that is run on as many simulations as specfied by the user. These workloads are usually suffixed with -uniform, which indicates that all nodes in the workload run the same job. An example of such a workload is firesim/deploy/workloads/linux-uniform.json.
  • Several different jobs, in which case there must be exactly as many jobs as there are running simulated nodes. An example of such a workload is firesim/deploy/workloads/ping-latency.json.

FireSim supports can take these workload definitions and perform two functions:

  • Building workloads using firesim/deploy/workloads/gen-benchmark-rootfs.py
  • Deploying workloads using the manager

In the following subsections, we will go through the two aforementioned example workload configurations, describing how these two functions use each part of the json file inline.

ERRATA: You will notice in the following json files the field “workloads” this should really be named “jobs” – we will fix this in a future release.

ERRATA: The following instructions assume the default buildroot-based linux distribution (br-disk). In order to customize Fedora, you should build the basic Fedora image (as described in Running Fedora on FireSim) and modify the image directly (or in QEMU). Imporantly, Fedora currently does not support the “command” option for workloads.

Uniform Workload JSON

firesim/deploy/workloads/linux-uniform.json is an example of a “uniform” style workload, where each simulated node runs the same software configuration.

Let’s take a look at this file:

{
  "benchmark_name" : "linux-uniform",
  "common_bootbinary" : "br-disk-bin",
  "common_rootfs"     : "br-disk.img",
  "common_outputs"    : ["/etc/os-release"],
  "common_simulation_outputs" : ["uartlog", "memory_stats.csv"]
}

There is also a corresponding directory named after this workload/file:

[email protected]:~/firesim-new/deploy/workloads/linux-uniform$ ls -la
total 4
drwxrwxr-x  2 centos centos   42 May 17 21:58 .
drwxrwxr-x 13 centos centos 4096 May 18 17:14 ..
lrwxrwxrwx  1 centos centos   41 May 17 21:58 br-disk-bin -> ../../../sw/firesim-software/images/br-disk-bin
lrwxrwxrwx  1 centos centos   41 May 17 21:58 br-disk.img -> ../../../sw/firesim-software/images/br-disk.img

We will elaborate on this later.

Looking at the JSON file, you’ll notice that this is a relatively simple workload definition.

In this “uniform” case, the manager will name simulations after the benchmark_name field, appending a number for each simulation using the workload (e.g. linux-uniform0, linux-uniform1, and so on). It is standard pratice to keep benchmark_name, the json filename, and the above directory name the same. In this case, we have set all of them to linux-uniform.

Next, the common_bootbinary field represents the binary that the simulations in this workload are expected to boot from. The manager will copy this binary for each of the nodes in the simulation (each gets its own copy). The common_bootbinary path is relative to the workload’s directory, in this case firesim/deploy/workloads/linux-uniform. You’ll notice in the above output from ls -la that this is actually just a symlink to br-disk-bin that is built by the FireSim Linux distro in firesim/sw/firesim-software.

Similarly, the common_rootfs field represents the disk image that the simulations in this workload are expected to boot from. The manager will copy this root filesystem image for each of the nodes in the simulation (each gets its own copy). The common_rootfs path is relative to the workload’s directory, in this case firesim/deploy/workloads/linux-uniform. You’ll notice in the above output from ls -la that this is actually just a symlink to br-disk.img that is built by the FireSim Linux distro in firesim/sw/firesim-software.

The common_outputs field is a list of outputs that the manager will copy out of the root filesystem image AFTER a simulation completes. In this simple example, when a workload running on a simulated cluster with firesim runworkload completes, /etc/os-release will be copied out from each rootfs and placed in the job’s output directory within the workload’s output directory (See the firesim runworkload section). You can add multiple paths here.

The common_simulation_outputs field is a list of outputs that the manager will copy off of the simulation host machine AFTER a simulation completes. In this example, when a workload running on a simulated cluster with firesim runworkload completes, the uartlog (an automatically generated file that contains the full console output of the simulated system) and memory_stats.csv files will be copied out of the simulation’s base directory on the host instance and placed in the job’s output directory within the workload’s output directory (see the firesim runworkload section). You can add multiple paths here.

ERRATA: “Uniform” style workloads currently do not support being automatically built – you can currently hack around this by building the rootfs as a single-node non-uniform workload, then deleting the workloads field of the JSON to make the manager treat it as a uniform workload. This will be fixed in a future release.

Non-uniform Workload JSON (explicit job per simulated node)

Now, we’ll look at the ping-latency workload, which explicitly defines a job per simulated node.

{
  "common_bootbinary" : "bbl-vmlinux",
  "benchmark_name" : "ping-latency",
  "deliver_dir" : "/",
  "common_args" : [],
  "common_files" : ["bin/pinglatency.sh"],
  "common_outputs" : [],
  "common_simulation_outputs" : ["uartlog"],
  "no_post_run_hook": "",
  "workloads" : [
    {
      "name": "pinger",
      "files": [],
      "command": "pinglatency.sh && poweroff -f",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "pingee",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-1",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-2",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-3",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-4",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-5",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    },
    {
      "name": "idler-6",
      "files": [],
      "command": "while true; do sleep 1000; done",
      "simulation_outputs": [],
      "outputs": []
    }
  ]
}

Additionally, let’s take a look at the state of the ping-latency directory AFTER the workload is built:

[email protected]:~/firesim-new/deploy/workloads/ping-latency$ ls -la
total 15203216
drwxrwxr-x  3 centos centos       4096 May 18 07:45 .
drwxrwxr-x 13 centos centos       4096 May 18 17:14 ..
lrwxrwxrwx  1 centos centos         41 May 17 21:58 bbl-vmlinux -> ../../../sw/firesim-software/images/br-disk-bin
-rw-rw-r--  1 centos centos          7 May 17 21:58 .gitignore
-rw-r--r--  1 centos centos 1946009600 May 18 07:45 idler-1.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:45 idler-2.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:45 idler-3.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:45 idler-4.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:45 idler-5.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:46 idler-6.ext2
drwxrwxr-x  3 centos centos         16 May 17 21:58 overlay
-rw-r--r--  1 centos centos 1946009600 May 18 07:44 pingee.ext2
-rw-r--r--  1 centos centos 1946009600 May 18 07:44 pinger.ext2
-rw-rw-r--  1 centos centos       2236 May 17 21:58 ping-latency-graph.py

First, let’s identify some of these files:

  • bbl-vmlinux: Just like in the linux-uniform case, this workload just uses the default Linux binary generated in firesim-software. Note that it’s named differently here, but still symlinks to br-disk-bin in firesim-software.
  • .gitignore: This just ignores the generated rootfses, which we’ll learn about below.
  • idler-[1-6].ext2, pingee.ext2, pinger.ext2: These are rootfses that are generated from the json script above. We’ll learn how to do this shortly.

Additionally, let’s look at the overlay subdirectory:

[email protected]:~/firesim-new/deploy/workloads/ping-latency/overlay$ ls -la */*
-rwxrwxr-x 1 centos centos 249 May 17 21:58 bin/pinglatency.sh

This is a file that’s actually committed to the repo, that runs the benchmark we want to run on one of our simulated systems. We’ll see how this is used soon.

Now, let’s take a look at how we got here. First, let’s review some of the new fields present in this JSON file:

  • common_files: This is an array of files that will be included in ALL of the job rootfses when they’re built. This is relative to a path that we’ll pass to the script that generates rootfses.

  • workloads: This time, you’ll notice that we have this array, which is populated by objects that represent individual jobs. Each job has some additional fields:

    • name: In this case, jobs are each assigned a name manually. These names MUST BE UNIQUE within a particular workload.
    • files: Just like common_files, but specific to this job.
    • command: This is the command that will be run automatically immediately when the simulation running this job boots up. This is usually the command that starts the workload we want.
    • simulation_outputs: Just like common_simulation_outputs, but specific to this job.
    • outputs: Just like common_outputs, but specific to this job.

In this example, we specify one node that boots up and runs the pinglatency.sh benchmark, then powers off cleanly and 7 nodes that just idle waiting to be pinged.

Given this JSON description, our existing pinglatency.sh script in the overlay directory, and the base rootfses generated in firesim-software, the following command will automatically generate all of the rootfses that you see in the ping-latency directory.

[ from the workloads/ directory ]
python gen-benchmark-rootfs.py -w ping-latency.json -r -b ../../sw/firesim-software/images/br-disk.img -s ping-latency/overlay

Notice that we tell this script where the json file lives, where the base rootfs image is, and where we expect to find files that we want to include in the generated disk images. This script will take care of the rest and we’ll end up with idler-[1-6].ext2, pingee.ext2, and pinger.ext2!

You’ll notice a Makefile in the workloads/ directory – it contains many similar commands for all of the workloads included with FireSim.

Once you generate the rootfses for this workload, you can run it with the manager by setting workload=ping-latency.json in config_runtime.ini. The manager will automatically look for the generated rootfses (based on workload and job names that it reads from the json) and distribute work appropriately.

Just like in the uniform case, it will copy back the results that we specify in the json file. We’ll end up with a directory in firesim/deploy/results-workload/ named after the workload name, with a subdirectory named after each job in the workload, which will contain the output files we want.