Final answer:
Demand cleaning in VM systems saves resources by only cleaning pages when needed and can improve overall performance, but may lead to delays when pages need to be cleaned upon request. This can potentially cause inconsistent performance and requires complex algorithms to predict which pages will be used. A trade-related analogy is a company that manufactures on demand, potentially causing delivery delays.
Step-by-step explanation:
When discussing VM (Virtual Machine) systems and their cleaning policies, the use of demand cleaning refers to the strategy of cleaning memory pages only when they are needed, rather than in advance. There are both pros and cons to using this method.
Pros of Demand Cleaning:
- It conserves resources by not cleaning pages until it is certain that they will be reused.
- Demand cleaning can lead to better performance for tasks that don't require constant access to cleaned pages.
- This method can adaptively allocate more time to actual computing tasks rather than cleaning.
Cons of Demand Cleaning:
- It can cause delays when accessing data because cleaning must occur at the moment the page is needed, leading to a potential performance hit.
- Inconsistent performance might result as tasks may run quickly when clean pages are available but slow down when pages must be cleaned on demand.
- More sophisticated algorithms are required to predict which pages will be needed soon, which can make the VM system more complex.
Trade-Related Analogy
Consider the roommate-cleaning scenario: If you clean only when necessary, you might save time initially, but when it's time to clean, it might take longer as the mess has accumulated, leading to delays. A similar trade-related analogy would involve a company that only manufactures products when orders are received, potentially delaying delivery times compared to a company that maintains an inventory of pre-manufactured products.