diff --git a/swh/scheduler/cli/simulator.py b/swh/scheduler/cli/simulator.py
index bade0d4..02280b7 100644
--- a/swh/scheduler/cli/simulator.py
+++ b/swh/scheduler/cli/simulator.py
@@ -1,68 +1,75 @@
 # Copyright (C) 2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import time
 
 import click
 
 from . import cli
 
 
 @cli.group("simulator")
 def simulator():
     """Scheduler simulator."""
     pass
 
 
 @simulator.command("fill-test-data")
+@click.option(
+    "--num-origins",
+    "-n",
+    type=int,
+    default=100000,
+    help="Number of listed origins to add",
+)
 @click.pass_context
-def fill_test_data_command(ctx):
+def fill_test_data_command(ctx, num_origins):
     """Fill the scheduler with test data for simulation purposes."""
     from swh.scheduler.simulator import fill_test_data
 
-    click.echo("Filling test data...")
+    click.echo(f"Filling {num_origins:,} listed origins data...")
     start = time.monotonic()
-    fill_test_data(ctx.obj["scheduler"])
+    fill_test_data(ctx.obj["scheduler"], num_origins=num_origins)
     runtime = time.monotonic() - start
     click.echo(f"Completed in {runtime:.2f} seconds")
 
 
 @simulator.command("run")
 @click.option(
     "--scheduler",
     "-s",
     type=click.Choice(["task_scheduler", "origin_scheduler"]),
     default="origin_scheduler",
     help="Scheduler to simulate",
 )
 @click.option(
     "--policy",
     "-p",
     type=click.Choice(["oldest_scheduled_first"]),
     default="oldest_scheduled_first",
     help="Scheduling policy to simulate (only for origin_scheduler)",
 )
 @click.option("--runtime", "-t", type=float, help="Simulated runtime")
 @click.pass_context
 def run_command(ctx, scheduler, policy, runtime):
     """Run the scheduler simulator.
 
     By default, the simulation runs forever. You can cap the simulated runtime
     with the --runtime option, and you can always press Ctrl+C to interrupt the
     running simulation.
 
     'task_scheduler' is the "classic" task-based scheduler; 'origin_scheduler'
     is the new origin-visit-aware simulator. The latter uses --policy to decide
     which origins to schedule first based on information from listers.
     """
     from swh.scheduler.simulator import run
 
     policy = policy if scheduler == "origin_scheduler" else None
     run(
         scheduler=ctx.obj["scheduler"],
         scheduler_type=scheduler,
         policy=policy,
         runtime=runtime,
     )