Difference between User Level thread and Kernel Level thread
Last Updated :
18 May, 2023
Introduction –
So in this article, we will see the overview of the User Level thread and Kernel Level thread. and also understand the basic required terms:
User-Level Thread-
The User-level Threads are implemented by the user-level software. the user-level threads are basically created and implemented by the thread library which OS provides as an API for creating the managing synchronizing threads. it is faster than the kernel-level threads, it is basically represented by the program counter, stack, register, and PCB.
Example – user threads library includes POSIX threads, Mach C-Threads
Kernel-Level Thread –
So, in terms of the Operating systems basically, the threads are the unit of execution within a process. and the kernel level threads are also kinds of threads which is directly handled via kernel threads management. The Kernel-level threads are directly handled by the OS directly whereas the thread’s management is done by the kernel.
In the Kernel Level Threads, Each thread is self-organizing and the kernel provides each thread with its own context with information about the thread’s status, such as its name, group, and priority.
Example – The example of Kernel-level threads are Java threads, POSIX threads, etc.
Difference between User-Level Thread V/S Kernel-Level Thread.
S. No. |
Parameters |
User Level Thread |
Kernel Level Thread |
1. |
Implemented by |
User threads are implemented by users. |
Kernel threads are implemented by Operating System (OS). |
2. |
Recognize |
The operating System doesn’t recognize user-level threads. |
Kernel threads are recognized by Operating System. |
3. |
Implementation |
Implementation of User threads is easy. |
Implementation of Kernel-Level thread is complicated. |
4. |
Context switch time |
Context switch time is less. |
Context switch time is more. |
5. |
Hardware support |
Context switch requires no hardware support. |
Hardware support is needed. |
6. |
Blocking operation |
If one user-level thread performs a blocking operation then the entire process will be blocked. |
If one kernel thread performs a blocking operation then another thread can continue execution. |
7. |
Multithreading |
Multithread applications cannot take advantage of multiprocessing. |
Kernels can be multithreaded. |
8. |
Creation and Management |
User-level threads can be created and managed more quickly. |
Kernel-level level threads take more time to create and manage. |
9. |
Operating System |
Any operating system can support user-level threads. |
Kernel-level threads are operating system-specific. |
10. |
Thread Management |
The thread library contains the code for thread creation, message passing, thread scheduling, data transfer, and thread destroying |
The application code does not contain thread management code. It is merely an API to the kernel mode. The Windows operating system makes use of this feature. |
11. |
Example |
Example: Java thread, POSIX threads. |
Example: Window Solaris. |
12. |
Advantages |
- User Level Threads are simple and quick to create.
- Can run on any operating system
- They perform better than kernel threads since they don’t need to make system calls to create threads.
- In user-level threads, switching between threads does not need kernel mode privileges.
|
- Scheduling multiple threads that belong to the same process on different processors is possible in kernel-level threads.
- Multithreading can be there for kernel routines.
- When a thread at the kernel level is halted, the kernel can schedule another thread for the same process.
|
13. |
Disadvantages |
- Multithreaded applications on user-level threads cannot benefit from multiprocessing.
- If a single user-level thread performs a blocking operation, the entire process is halted.
|
- Transferring control within a process from one thread to another necessitates a mode switch to kernel mode.
- Kernel-level threads take more time to create and manage than user-level threads.
|
14. |
Memory management |
In user-level threads, each thread has its own stack, but they share the same address space. |
In kernel-level threads have their own stacks and their own separate address spaces, so they are better isolated from each other. |
15. |
Fault tolerance |
User-level threads are less fault-tolerant than kernel-level threads. If a user-level thread crashes, it can bring down the entire process. |
Kernel-level threads can be managed independently, so if one thread crashes, it doesn’t necessarily affect the others. |
16. |
Resource utilization |
User-level threads don’t take full advantage of the system resources, As they don’t have direct access to the system-level features like I/O operations |
It can access to the system-level features like I/O operations.So it can take full Advantages of System Resources. |
17. |
Portability |
User-level threads are more portable than kernel-level threads. |
Kernel-level threads are less portable than User-level threads. |
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