guideperformanceReviewed July 15, 2026

Measure before tuning

Performance work begins with a workload statement and synchronized host/guest evidence. Change one constraint at a time and preserve a rollback definition. Baseline capture Record the experiment Capture workload version,

baselinemetricsperftuning

Performance work begins with a workload statement and synchronized host/guest evidence. Change one constraint at a time and preserve a rollback definition.

Baseline capture

BASH

virsh domstats guest01 --vcpu --balloon --block --interface
pidstat -p $(pgrep -f 'qemu-system.*guest=guest01') 1
mpstat -P ALL 1
iostat -xz 1

Record the experiment

Capture workload version, duration, host load, guest XML hash, storage path, network path, percentiles, errors, and saturation indicators. A faster average with worse tail latency may be a regression.

Reversible change

BASH

virsh dumpxml guest01 --inactive > /root/guest01.performance-baseline.xml
sha256sum /root/guest01.performance-baseline.xml

Reject tuning folklore that does not identify a measured constraint, expected mechanism, success threshold, and rollback trigger.