https://github.com/brendangregg/wrmsrbench
WRMSR micro benchmark
https://github.com/brendangregg/wrmsrbench
Last synced: 2 months ago
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WRMSR micro benchmark
- Host: GitHub
- URL: https://github.com/brendangregg/wrmsrbench
- Owner: brendangregg
- Created: 2019-02-19T18:15:08.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2019-02-19T18:16:19.000Z (over 6 years ago)
- Last Synced: 2025-03-25T06:33:00.417Z (3 months ago)
- Language: C
- Size: 1000 Bytes
- Stars: 7
- Watchers: 1
- Forks: 1
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# wrmsrbench
Microbenchmark for the wrmsr instruction.
This loads a kernel module since wrmsr must run as ring 0 or 1. The MSR written can be modified in the source: be careful, as many will harm the system: eg, changing voltages and writing to firmware. I'm guessing that worst cases include bricking a system, and setting it on fire.
```
# make
[...]
# make run
insmod wrmsrbench.ko
rmmod wrmsrbench
dmesg | tail -1
[530060.004103] wrmsrbench: 58 ns per instruction, 2000000 instructions
perf stat -a -- date > /dev/null 2>&1 # reset MSRs
```
That run showed 58 nanoseconds per wrmsr. It works by loading a kernel module which runs the benchmark in its init routine, writes to dmesg, and then unloads the module. We fetch the output from dmesg.
WARNING: This is dangerous software. Do not use unless you know and accept the risks of writing to MSRs, which include rebooting or damaging systems.