fork_vs_thread/README.md

Fork vs Threads Experiments

This project compares Linux process creation (fork) versus thread creation (pthreads). It includes timing, scaling, and stress tests to show performance differences and system limits.

How to run

Run all experiments (safe by default):

bash run_all_experiments.sh

Run individual experiments (examples):

bash creation_time_experiment/bash_test_iter.sh
bash thread_recursive_scaling/run_thread_recursive.sh

Enable the dangerous stress test (timeboxed):

ALLOW_DANGEROUS=1 FORK_BOMB_SECONDS=5 bash run_all_experiments.sh

Key Commands for lifting linux kernel restrictions on alpine linux for threads & processes:

# Lift shell nproc limit
ulimit -u unlimited

# Raise kernel PID/thread caps (temporary until reboot)
sysctl -w kernel.pid_max=131072
sysctl -w kernel.threads-max=131072


# cgroup v2 setup (Alpine Linux)
mkdir -p /sys/fs/cgroup/test
echo max > /sys/fs/cgroup/test/pids.max
echo $$ > /sys/fs/cgroup/test/cgroup.procs

Clean-up commands run after tests:

# Cleanup to make it non-persistent (move out, then delete)
echo $$ > /sys/fs/cgroup/cgroup.procs
rmdir /sys/fs/cgroup/test

Potential dangers

• The fork bomb can freeze your machine or make it unresponsive by exhausting processes/threads.
• You may need elevated limits (ulimit or sysctl) to run high-stress tests.
• Running heavy tests on shared systems or laptops can disrupt other users and risk data loss if the system becomes unstable.

If you are unsure, do not enable the dangerous tests.

It is very important to run above test in virtual machine to avoid some of the potential dangers