How to benchmark CPU performance on Linux

Benchmarking CPU performance on Linux provides a repeatable baseline for comparing systems, sizing virtual machines, or checking whether firmware, kernel, power-profile, or cooling changes reduced compute throughput. A short synthetic run is often the quickest way to confirm whether slower builds, compiles, or batch jobs are actually tied to processor performance.

sysbench cpu measures how quickly the system can calculate prime numbers with a chosen number of worker threads. The result includes events per second, total completed events, and latency percentiles, which makes it useful for comparing single-thread responsiveness, all-thread throughput, and sustained performance with the same workload.

The steps below use sysbench on Ubuntu 24.04 LTS and were validated against the current sysbench cpu defaults. Run the benchmark on an otherwise idle system, keep the same power and cooling conditions between runs, and reuse the same thread count and test length when comparing one machine or configuration against another.

Steps to benchmark CPU performance in Linux with sysbench:

Check how many CPU threads the current environment makes available to the benchmark.
```
$ nproc
10
```
Use this value for the all-thread runs so the workload matches the CPUs currently exposed to the host, guest, or container.

Related: How to check CPU information in Linux

Run a single-thread baseline test.

$ sysbench cpu run
sysbench 1.0.20 (using system LuaJIT 2.1.0-beta3)

Running the test with following options:
Number of threads: 1
Initializing random number generator from current time


Prime numbers limit: 10000

Initializing worker threads...

Threads started!

CPU speed:
    events per second:  7881.02

General statistics:
    total time:                          10.0001s
    total number of events:              78819

Latency (ms):
         min:                                    0.11
         avg:                                    0.13
         max:                                   25.29
         95th percentile:                        0.13
         sum:                                 9973.69

Threads fairness:
    events (avg/stddev):           78819.0000/0.00
    execution time (avg/stddev):   9.9737/0.00

The default sysbench cpu run uses one worker thread for 10 seconds with a prime limit of 10000, which makes it a quick single-thread baseline.

Run the same test across all available threads.

$ sysbench cpu --threads=10 run
sysbench 1.0.20 (using system LuaJIT 2.1.0-beta3)

Running the test with following options:
Number of threads: 10
Initializing random number generator from current time


Prime numbers limit: 10000

Initializing worker threads...

Threads started!

CPU speed:
    events per second: 46804.10

General statistics:
    total time:                          10.0003s
    total number of events:              468081

Latency (ms):
         min:                                    0.12
         avg:                                    0.21
         max:                                  101.26
         95th percentile:                        0.45
         sum:                                99721.06

Threads fairness:
    events (avg/stddev):           46808.1000/2896.48
    execution time (avg/stddev):   9.9721/0.01

Replace 10 with the value reported by nproc on the current system. Compare this result with the single-thread baseline to see how well the workload scales across the available threads.

Run a longer all-thread test to check whether performance drops under sustained load.

$ sysbench cpu --threads=10 --time=15 run
sysbench 1.0.20 (using system LuaJIT 2.1.0-beta3)

Running the test with following options:
Number of threads: 10
Initializing random number generator from current time


Prime numbers limit: 10000

Initializing worker threads...

Threads started!

CPU speed:
    events per second: 40067.37

General statistics:
    total time:                          15.0003s
    total number of events:              601087

Latency (ms):
         min:                                    0.12
         avg:                                    0.25
         max:                                  175.03
         95th percentile:                        0.46
         sum:                               149589.60

Threads fairness:
    events (avg/stddev):           60108.7000/2604.52
    execution time (avg/stddev):   14.9590/0.02

Longer all-core runs can expose power limits, clock reductions, and thermal throttling, so sustained scores are often lower than short burst scores on the same hardware.

Compare the events per second, total number of events, and 95th percentile from each run to judge baseline responsiveness, all-thread throughput, and whether the system slows down as the benchmark continues.

Keep threads and time identical between repeated runs so the results stay comparable.