Chapter 7: Data Collection Flashcards
(31 cards)
What are the five types of data needed for SPE
- Key Performance scenarios
- Performance objectives
- Execution Environment
- Software Resource Requirements
- Computer Resource Requirements
What are heavy hitters?
Functions that take up the most resources
What do we need to estimate in key performance scenarios?
- Workload intensity
- Arrival rate of requests
- Number of concurrent users
What does the execution environment consist of?
- Hardware and network
- Operating system
- Database usage
- Other software that uses resources
How do we estimate software resource requirements?
Can use work units
What are the types of computer resource requirements?
- CPU time for work units
- Number of I/O
- Message size
How do we map software resource requirements into computer resource requirements?
Processing overhead matrix
What is a walkthrough?
Informal review where member of development team discusses system
What is a performance walkthrough?
Similar to walkthrough except goal is to gather the information needed to construct performance models.
What is a user representative?
Provides data on how the system will be used, how often and typical usage conditions
What is a system architect
Provides overview of system and its components along with use cases
What is a performance specialist?
Someone who is familiar with measurements of target configuration and can either provide data or perform measurements to get data.
When should performance walkthroughs be conducted?
- Early stages, should be part of overall feasibility study to see if the project can continue.
- When system evolves. The frequency of performing walkthroughs depends on performance risk.
Are resource requirements the most difficult specifications to esimate?
True
What are use measurements?
- Start with an estimate
- Use model results to study accuracy of model results to estimates
- Modify it with accurate estimates as soon as possible
Continue to evaluate the system as it evovles
What are study measurements?
Study similar systems to develop a frame of reference to estimate resource requirements
What should you do if you haven’t participated in SPE studies before?
Use a mentor to assist and advise you on resource estimates in initial walkthroughs
When uncertainty is an issue in measurements what should be used?
Use best-worse case estimates
- First use best case as if that doesn’t work then no point in continuing
- Use worst case estimates to find anomalies in system.
What happens if worst-case estimates pass the system?
No point in developing more precise metrics.
What should be estimated?
- Dominant Resource Usage
- I/O Requirements
- Network messages
What are dominant resources?
Resources that account for most of elapsed time in scenario
What do we need to estimate I/O Requirements?
- Number of physical I/O
- I/O Service times
- Random or sequential access
How do we estimate number of physical I/O?
- First method: Indirectly method of estimating I/O. Estimate the logical I/Os and then estimate hit ratio
- Second method: Directly estimate I/O. Estimate which I/O requests might be stored in a cache/buffer, count only ones that would access physical I/O.
How does read random access effect number of I/O?
For read requests that random access an indexed file or table the number of logical I/O is i+1,
where i is the number of files in file index and
1 is the I/O to read the data record
