CPU time
Let an agent explain CPU time and how it differs from elapsed time, relay how it is measured and reported on major operating systems, describe its use in performance analysis and billing, and interpret user versus system time.
Bundle → Layer → Finding → Questions Filled
4 bundles · 8 layers · 8 findings · 16 questions
Understand What CPU time is.
Definition
Definition.
Definition
Definition.
- What is CPU time, and how does it differ from wall-clock time and CPU utilisation? definition
- Is the question about CPU time, elapsed time or utilisation? boundary
Split
User and system time.
Split
Split.
- What do user and system time mean, and what does a high system share indicate? definition
- Which entry fits the specific component? action
Measure Measurement.
Tools
Tools.
Tools
Tools.
- How is CPU time measured with time, top, ps, perf, Task Manager and profilers? action
- Which references are standard? provenance
Code
In code.
Code
Code.
- How do programs read their own CPU time through POSIX and language APIs? action
- Which entry fits the specific API? action
Apply Applications.
Performance
Performance analysis.
Performance
Performance.
- How is CPU time used to find bottlenecks and compare implementations? provenance
- Which sources are cited? provenance
Billing
Scheduling and billing.
Billing
Billing.
- How do schedulers, quotas and cloud providers use CPU time? provenance
- Which entry fits cloud computing pricing? action
Context History and pitfalls.
History
History.
History
History.
- How did CPU time accounting develop with time-sharing systems? provenance
- Which entry fits the history of time-sharing? action
Pitfalls
Pitfalls.
Pitfalls
Pitfalls.
- What pitfalls arise with multi-core totals, virtualisation and frequency scaling? provenance
- Which entry fits benchmarking? action
Classifiers Filled
- Family
- Thing Registry
- Category
- Cross-cutting context
- Entry kind
- thing
- Plane
- XCT
- Domain
- XCT.QTY
What it is Filled
The amount of time for which a central processing unit was used to execute instructions of a program or process, measured in seconds or clock ticks and separated into user time spent in the program and system time spent in the kernel on its behalf, as distinct from wall-clock elapsed time that includes waiting for input, output and other processes; CPU time is a performance metric, a billed resource in shared and cloud computing, and a basis for scheduling and quotas.
Why it exists Filled
Let an agent explain CPU time and how it differs from elapsed time, relay how it is measured and reported on major operating systems, describe its use in performance analysis and billing, and interpret user versus system time.
Distinguishing features Filled
- Excludes waiting time
- User and system split
- Can exceed elapsed time with multiple cores
- Billing basis
What robots and AI may and may not do Filled
Must not
- Report a benchmark figure without the hardware, load and measurement method it came from.
- Present CPU time as wall clock time or the reverse in billing or performance claims.
- Read process accounting data on systems the agent does not administer.
- Use process timing data to monitor individual workers' activity without their knowledge.
Only with a human decision
- Using CPU accounting data for billing or for assessing a person's work.
May
- Measure and report CPU time for processes on systems the agent is authorized to observe.
- Explain the difference between CPU time, wall clock time and elapsed time in benchmarks.
- Use CPU accounting to find inefficiency in code the agent is asked to improve.
Moral aspects Filled
- Metered compute is billed from these figures, so measurement choices affect what people pay.
- Process accounting on shared systems can reveal what individuals are doing.
Who is affected
- Users billed for compute
- Workers on monitored systems
- Operators of shared systems
Owners Filled
Steward
The operator of the system that records it.
Links to other meta-models Filled
parent
- Q107715 - registry parent class
- Q7168241 - registry parent class
- Q771906 - registry parent class
related
- performance metric - in registry terms
- system resource - in registry terms
- physical quantity - in registry terms
- elapsed real time - or wall-clock time
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.cpu-time
- Wikidata: Q1146920 (https://www.wikidata.org/wiki/Q1146920)
- POSIX: times() and getrusage() measurement interfaces
Direct properties not applicable Not applicable
- unit: seconds or clock ticks unit
- POSIX clock tick: often 100 per second - CLK_TCK, varies
Plane XCT: no invented physical properties.
Recognition optional Filled
- Processor time consumed by a process
- User time, system time, total CPU time; per-thread and per-core accounting
- Wall-clock time includes waiting; CPU utilisation is a percentage; core-hours are billing units
- Not a visible object; numbers in tools such as time, top and task managers.
Capabilities and actions required Filled
- explain the concept
- relay measurement tools
- describe performance and billing use
- interpret user and system time
Hazards and failure modes required Filled
- Confusing CPU time with elapsed time
- Misreading multi-core totals
- Accounting differences across systems
Standards and interfaces required Filled
- POSIX interfaces for process times
- Cloud provider billing definitions
- No legal regulation
Context of use required Filled
- Measuring processor usage by programs.
- user CPU time
- system CPU time
- per-process, per-thread and per-core CPU time
- CPU time as a scheduling quota
- core-hours and vCPU-seconds in cloud billing
Sources Filled
- Wikidata item Q1146920: CPU time - identity and sense of the item
- Wikipedia: CPU time - general description of the item
Open questions
- Should elapsed real time be a separate entry?
- How should OS documentation be linked?
- How should cloud billing units be recorded?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q1146920/spec.json