34 Questions
What are some common ways to measure computer system performance?
By using response time and throughput
Which of the following is an incorrect statement about measuring computer system performance?
Performance should always be measured in terms of clock cycles
In the context of measuring performance, which statement is true?
Improving throughput may not necessarily enhance response time
Which parameter is used to calculate Throughput in a computer system?
Instructions per second
What is Amdahl’s Law primarily concerned with?
Balancing the impact of parallelization on overall system performance
Which parameter is commonly used to measure Processor Performance?
$clock speed \times number \ of \ cores$
What type of problem is response time in this model?
Maximization problem
How can throughput generally be enhanced according to the text?
By adding extra hardware
What does the curve in Figure 1.15 illustrate?
Trade-off between throughput and response time
What is the key focus of performance measurement discussed in the text?
Total time of user's tasks completion
How does the text suggest improving response time when task numbers are high?
Through parallelization of tasks
What is the main challenge in reducing response time according to the text?
Optimizing architecture and technology
What is the formula for speedup when using p processors according to Eq.(1.5)?
S(p) = T (1) / T (p)
What does Amdahl's Law primarily focus on?
Improving single-threaded performance
Which scenario indicates a super-linear speedup?
S(p) > p
What aspect usually leads to a super-linear speedup in performance?
Non-optimal serial algorithm
In measuring performance, what does an improvement in Speedup(E) indicate?
Increased performance with the same execution time
Which factor contributes to the theoretical linear speedup scenario according to the text?
Optimal serial algorithm implementation
What are two common performance measures used in a system?
Response time and throughput
Does increasing throughput always lead to an improvement in response time?
No
Does reducing response time always result in an improvement in throughput?
No
What is one key focus of Amdahl's Law?
Identifying the potential speedup in a system by focusing on the parallelizable portion of a task
How can the concept of speedup be improved in performance measurement?
By enhancing parallel execution and reducing the impact of sequential portions of tasks
What does the curve in Figure 1.15 typically illustrate in the context of performance measurement?
The impact of parallelization on overall system speedup
Explain the trade-off between throughput and response time as described in the text, and describe the curve illustrated in Figure 1.15.
The text states that there is a trade-off between throughput and response time. As the throughput is maximized, the response time is increased. The curve illustrated in Figure 1.15 shows this trade-off - as throughput is enhanced, response time is increased.
Discuss the challenges in reducing response time according to the text, and explain how the text suggests improving response time when task numbers are high.
The text states that response time is much harder to reduce than throughput. To improve response time, it is necessary to consider optimizing the architecture or even the implementing technology. The text also suggests that it is possible to improve the response time when the task number is high and intermediate relevant results are produced, through parallelization.
Describe the different ways the text suggests for enhancing throughput in a computer system.
The text states that generally, the throughput can be enhanced by adding extra hardware. This acts by reducing the latency with respect to the load, as shown in Figure 1.14 where having more than one queue can enhance throughput.
Discuss the key focus of performance measurement as described in the text, and identify some common ways to measure computer system performance.
The text states that the most important fact in considering performance is the total time of user's tasks completion. Therefore, the faster computer is always the one that responds to the user in less time. The text does not provide any specific details about common ways to measure computer system performance.
What is the primary factor that determines whether enhancements lead to a super-linear speedup (S(p) > p) or a theoretical linear speedup (S(p) ≤ p)?
The primary factor is whether there is a non-optimal serial algorithm or hardware features that place the serial algorithm at a disadvantage. A non-optimal serial algorithm can lead to a super-linear speedup when parallelized.
Based on the provided equations, how would you calculate the speedup achieved when using 4 processors, if the serial execution time is 100 seconds and the parallel execution time with 4 processors is 30 seconds?
Using Eq.(1.5): S(p) = T(1) / T(p) S(4) = T(1) / T(4) = 100 / 30 = 3.33
According to Amdahl's Law, what should be the primary focus when trying to improve the performance of a computer system?
Amdahl's Law suggests focusing on the most frequently used or 'common case' parts of the system for possible enhancements.
Explain how the concepts of throughput enhancement and response time reduction relate to each other, and what trade-offs might be involved in prioritizing one over the other.
Throughput enhancement focuses on improving the overall amount of work completed per unit time, while response time reduction aims to decrease the time taken to complete individual tasks. Prioritizing throughput may lead to higher overall productivity but longer wait times for individual tasks. Conversely, prioritizing response time may improve user experience but potentially at the cost of overall throughput.
Provide an example scenario where a super-linear speedup (S(p) > p) might occur, and explain the underlying reasons for this phenomenon based on the information given in the text.
A super-linear speedup might occur when parallelizing a computationally intensive algorithm that has a non-optimal serial implementation. For example, if the serial algorithm has a poor memory access pattern or does redundant computations, parallelizing it could lead to better utilization of hardware resources and cache locality, resulting in a speedup greater than the number of processors used.
Based on the information provided, what potential strategies or techniques could be employed to improve both throughput and response time in a computer system simultaneously?
The text does not provide specific strategies for improving both throughput and response time simultaneously. However, potential approaches could include optimizing the most common case scenarios through parallelization, improving cache and memory performance, and utilizing hardware accelerators or specialized processing units for specific tasks.
Study Notes
Measuring Performance
- Measuring performance is crucial in computer systems, and it raises questions about how to assess the impact of a computer performance improvement.
- Performance can be measured using response time and throughput, where response time is the time between the start and completion of an event, and throughput is the total amount of work done in a given timeframe.
Performance Measures
- Response time and throughput are two important performance measures.
- Response time is a minimization problem, where the goal is to minimize the time taken to complete a task or task set.
- Throughput is a maximization problem, where the goal is to maximize the amount of work done in a given timeframe.
Throughput Enhancement
- Throughput can be enhanced by adding extra hardware, which reduces latency with respect to the load.
- However, response time is harder to reduce and requires optimization of the architecture or implementing technology.
Throughput Enhancement vs. Response Time
- There is a trade-off between throughput and response time, where increasing throughput can lead to increased response time.
- The curve in Fig. 1.15 illustrates this trade-off, showing that as throughput is maximized, response time is increased.
Performance and User Tasks
- The most important factor in performance is the total time it takes to complete user tasks.
- A faster computer is one that responds to the user in less time, and this can be achieved through parallelization when the task number is high and intermediate relevant results are produced.
Speedup
- Speedup is the observed improvement in performance due to an enhancement E.
- Speedup is measured as the ratio of execution times, as shown in Eqs. (1.3) and (1.4).
- Theoretically, most cases will have a linear speedup, but some cases can present a super-linear speedup.
Possible Targets and Strategies
- There are several techniques, components, and communication interconnections that can be targeted for enhancement.
- The common case and Amdahl's Law theory are key in determining what to prioritize for possible enhancements.
Explore the importance of measuring system performance and learn about different performance metrics like clocks and FLOPS. Test your knowledge on assessing the impact of computer performance improvements and whether performance should be measured based on time taken to complete a task.
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