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stress-ng vs sysbench

#testing

stress-ng vs sysbench

A practical guide to two common Linux load-generation tools: what each one does, how they differ, and when to use them.

1. Overview

stress-ng sysbench
Primary goal Stress testing and fault finding Benchmarking and performance measurement
One-line summary Designed to break things Designed to measure things

2. stress-ng

stress-ng loads a system's hardware and kernel interfaces in many different ways. It is a much larger successor to the original stress tool.

Core features

  • Large set of stressors: 300+ built-in tests, each exercising a specific part of the system.
  • CPU stress: Many compute methods (integer, floating point, matrix, FFT, bit operations, hashing) via --cpu and --cpu-method.
  • Memory stress: Virtual memory, cache, memory copy, mmap, page faults, NUMA, via --vm, --cache, --memcpy, --mmap.
  • I/O and filesystem stress: Disk reads/writes, fsync, file locking, directory operations, via --hdd, --io, --dir.
  • Kernel interface stress: Syscalls, signals, pipes, sockets, semaphores, message queues, futexes, threads, context switches, scheduler.
  • Network stress: Socket and protocol-level tests.
  • Device and driver stress: ioctl, /dev, /proc and /sys interfaces.

Control and configuration

Option Purpose
--cpu 4 / --cpu 0 Number of workers (0 = all online CPUs)
--timeout 60s Stop after a set time
--cpu-ops N Stop after N operations
--cpu-load 50 Target a CPU utilization percentage
--class cpu Run a group of stressors (cpu, memory, io, scheduler, ...)
--all, --random, --sequential Permutation modes
-x Exclude specific stressors

Measurement and reporting

  • Bogo ops: A rough throughput measure, useful for same-machine comparison but not a formal benchmark.
  • Metrics: --metrics / --metrics-brief for summaries; --yaml or --log-file to save results.
  • Thermal and perf data: --thermalstat, --vmstat, --perf.
  • Verification: --verify checks that results are correct, helping catch hardware faults or memory errors.

Common uses

  • Burn-in and stability testing of new hardware
  • Checking cooling and thermal throttling
  • Finding kernel bugs or race conditions
  • Testing behavior under resource pressure (CPU, RAM, I/O)

Example commands 

# Stress all CPUs for 60 seconds with a summary
stress-ng --cpu 0 --timeout 60s --metrics-brief

# 4 CPU workers, 2 VM workers using 1GB each, 1 disk worker
stress-ng --cpu 4 --vm 2 --vm-bytes 1G --hdd 1 --timeout 120s --metrics-brief

# Run every CPU-class stressor in turn
stress-ng --class cpu --sequential 0 --timeout 30s
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Caution: stress-ng can make a system unresponsive, overheat, or crash, and some stressors can fill disks or trigger the OOM killer. Use it on test machines or with sensible limits, not carelessly on production.

3. sysbench

sysbench is a scriptable benchmark tool that produces repeatable performance numbers for CPU, memory, disk, threads, and databases.

Core features

  • CPU: Prime number computation benchmark.
  • Memory: Read/write throughput tests.
  • File I/O: Sequential and random read/write tests.
  • Threads and mutex: Scheduler and locking performance.
  • Database (OLTP): Workloads for MySQL and PostgreSQL.
  • Lua scripting: Write custom workloads.

Example commands 

# CPU benchmark
sysbench cpu --threads=4 --time=30 run

# Memory throughput
sysbench memory --threads=4 run

# File I/O
sysbench fileio --file-total-size=2G prepare
sysbench fileio --file-total-size=2G --file-test-mode=rndrw run
sysbench fileio --file-total-size=2G cleanup
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4. Key Differences

Aspect stress-ng sysbench
Purpose Stress testing, fault finding Benchmarking, performance comparison
Scope Very broad (300+ stressors) Narrow: CPU, memory, file I/O, threads, database
Output Bogo ops (rough, same-machine only) Events/sec, latency percentiles, MiB/sec
Database testing None Strong (OLTP for MySQL/PostgreSQL)
Correctness checking Yes (--verify) No, measures speed only
Extensibility Modify the C source Lua scripts

5. Which One Should You Use?

Goal Recommended tool
Burn-in, thermal, or stability testing stress-ng
Kernel bug hunting stress-ng
Comparing two servers or VM sizes sysbench
Measuring the effect of tuning changes sysbench
Database server performance sysbench

Using them together

The two tools complement each other:

  1. Run stress-ng to confirm the system stays stable under heavy load.
  2. Run sysbench to record how fast the system actually is.

6. Summary

  • stress-ng answers: "Does this system survive heavy load?"
  • sysbench answers: "How fast is this system?"

References:

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