Linux Server / Performance, Capacity & Containers
Find a single busy Linux CPU hidden by the host average
A service can bottleneck on one thread while overall CPU utilization looks modest. Observe per-processor activity during the symptom.
Environment and inputs: Linux server baseline · Ubuntu 24.04 LTS / RHEL 9-style systems. Use the specified distribution, init system and installed tool; service names, privileges and supported options can differ.
Start with this check
Confirm the host, shell and access role. Replace sample names, paths, domains and interfaces with approved targets. These are diagnostic commands; assess policy and workload impact before making changes.
mpstat -P ALL 1 5Read the result
With sysstat installed, the output reports timed CPU activity per logical processor. Interrupt, steal and other fields provide different context from application user CPU.
Resolve and verify
Match the imbalance with process threads and workload design. Tune serial work or scheduling only after confirming the application's actual constraint.
Before changing production
Do not assume more vCPUs will accelerate a single-threaded operation or pin processes without NUMA and workload testing.