Advantages of user-level threads include:
- Theoretically greater performance, as the OS does not need to perform expensive context switches
every time a thread changes.
- More configurable, as you are not tied to the kernel to decide a scheduling algorithm, nor do you
require kernel support for multiple threads.
Disadvantages of user-level threads include:
- Realistically worse performance, because many threads require a context switch regardless (say a
syscall is called, such as on an I/O event). This will force a switch into kernel mode and BLOCK every
single other user-level thread in that process from running, because the kernel treats the entire user-
space of threads as a single process.
- User level threads are generally co-operative rather than pre-emptive, so must manually yield() to
return control back to the dispatcher – a thread that does not do this may monopolise the CPU.
- I/O must be non-blocking – this requires extra checking just in case there is an action that should block.
- We cannot take advantage of multiprocessors, since the kernel sees one process with one thread.
Titany answered the question on April 26, 2022 at 05:11
- Describe how a multi-threaded application can be supported by a user-level threads package. It may be helpful to consider (and draw) the components of such...(Solved)
Describe how a multi-threaded application can be supported by a user-level threads package. It may be helpful to consider (and draw) the components of such a package, and the function they perform
Date posted: April 26, 2022. Answers (1)
- What is a process? What are attributes of a process?(Solved)
What is a process? What are attributes of a process?
Date posted: April 26, 2022. Answers (1)
- Multi-programming (or multi-tasking) enables more than a single process to apparently execute simultaneously. How is this achieved on a uniprocoessor?
(Solved)
Multi-programming (or multi-tasking) enables more than a single process to apparently execute simultaneously. How is this achieved on a uniprocoessor?
Date posted: April 25, 2022. Answers (1)
- Describe the three state process model, describe what transitions are valid between the
three states, and describe an event that might cause such a transition(Solved)
Describe the three state process model, describe what transitions are valid between the
three states, and describe an event that might cause such a transition
Date posted: April 25, 2022. Answers (1)
- Is putting security checks in the C library a good or a bad idea? Why?
(Solved)
Is putting security checks in the C library a good or a bad idea? Why?
Date posted: April 25, 2022. Answers (1)
- Why must the operating system be more careful when accessing input to a system call (or
producing the result) when the data is in memory...(Solved)
Why must the operating system be more careful when accessing input to a system call (or
producing the result) when the data is in memory instead of registers?
Date posted: April 25, 2022. Answers (1)
- Using a simple system call as an example (e.g. getpid, or uptime), describe what is
generally involved in providing the result, from the point of...(Solved)
Using a simple system call as an example (e.g. getpid, or uptime), describe what is
generally involved in providing the result, from the point of calling the function in the C
library to the point where that function returns
Date posted: April 25, 2022. Answers (1)
- Describe the two general roles of an operating system, and elaborate why these roles are
important(Solved)
Describe the two general roles of an operating system, and elaborate why these roles are
important
Date posted: April 25, 2022. Answers (1)
- A computer had the following characteristics:
- Artificial intelligence
- Connectivity to the internet
- Superior hardware and software (i.e. high processing speed and storage capacity)
- Low emission...(Solved)
A computer had the following characteristics:
- Artificial intelligence
- Connectivity to the internet
- Superior hardware and software (i.e. high processing speed and storage capacity)
- Low emission of heat
- Smaller in size
State the generation described above.
Date posted: July 23, 2021. Answers (1)
- Name three non electronic tools that were used before the invention of electronic computers.(Solved)
Name three non electronic tools that were used before the invention of electronic computers.
Date posted: July 23, 2021. Answers (1)
- Write the following acronyms in full.
i. ICT
ii. CPU
iii. VLSI
iv. UPS(Solved)
Write the following acronyms in full.
i. ICT
ii. CPU
iii. VLSI
iv. UPS
Date posted: July 23, 2021. Answers (1)
- Give the correct name for the following descriptions.
i. A device that process user input to give out an output that is meaningful to the user.
ii....(Solved)
Give the correct name for the following descriptions.
i. A device that process user input to give out an output that is meaningful to the user.
ii. Raw facts that do not have much meaning to the user.
iii. The result obtained after processing.
Date posted: July 23, 2021. Answers (1)
- Define the term troubleshooting as used in operating systems.(Solved)
Define the term troubleshooting as used in operating systems.
Date posted: July 23, 2021. Answers (1)
- Explain how you can partition a hard disk into partitions.(Solved)
Explain how you can partition a hard disk into partitions.
Date posted: July 23, 2021. Answers (1)
- What is a startup disk?(Solved)
What is a startup disk?
Date posted: July 23, 2021. Answers (1)
- Explain how you would create backup using Windows back-up using utility.(Solved)
Explain how you would create backup using Windows back-up using utility.
Date posted: July 23, 2021. Answers (1)
- You have realized that your floppy disk is limited in storage space and you would wish to create more space.
Which tool in Windows would you...(Solved)
You have realized that your floppy disk is limited in storage space and you would wish to create more space.
Which tool in Windows would you use?
Date posted: July 23, 2021. Answers (1)
- Explain how you would move the taskbar to the top of the desktop.(Solved)
Explain how you would move the taskbar to the top of the desktop.
Date posted: July 23, 2021. Answers (1)
- Define the start menu and explain the common start menu items.(Solved)
Define the start menu and explain the common start menu items.
Date posted: July 23, 2021. Answers (1)
- Draw the information organization tree diagram.(Solved)
Draw the information organization tree diagram.
Date posted: July 23, 2021. Answers (1)