•No special support needed from the kernel (use any Unix)
•Thread creation and context switch are fast (no syscall)
•Defines its own thread model and scheduling policies
User-level threads have the advantage of being lightweight and can be managed without kernel intervention, allowing for faster thread switching. However, they are limited in their ability to utilize multiple processors efficiently and can be blocked by system calls made by a single thread. Kernel-level threads, on the other hand, offer better performance on multi-core systems and can take advantage of kernel features, but they are heavier in terms of resource consumption and switching between threads can be slower due to kernel involvement.
threads are the light weight process or it is a part of the process which can execute simulteniously by sharing systm resources.... two types of thread 1.user level thread 2.kernel level thread
Context switching between kernel threads typically requires saving the value of the CPU registers from the thread being switched out and restoring the CPU registers of the new thread being scheduled.
KERNEL In computing, the kernel is the central component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).
The resources that are shared by all threads of a process in Operating SystemsareMain memoryInput Output DevicesInput Output ChannelsFiles
user level theads are not tranparent to kernel level threads.
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POSIX threads are user level threads, because had a interface library and the operating systems don't control his ejecution and does not know
There are two distinct models of thread controls, and they are user-level threads and kernel-level threads. The thread function library to implement user-level threads usually runs on top of the system in user mode. Thus, these threads within a process are invisible to the operating system. User-level threads have extremely low overhead, and can achieve high performance in computation. However, using the blocking system calls like read(), the entire process would block. Also, the scheduling control by the thread runtime system may cause some threads to gain exclusive access to the CPU and prevent other threads from obtaining the CPU. Finally, access to multiple processors is not guaranteed since the operating system is not aware of existence of these types of threads. On the other hand, kernel-level threads will guarantee multiple processor access but the computing performance is lower than user-level threads due to load on the system. The synchronization and sharing resources among threads are still less expensive than multiple-process model, but more expensive than user-level threads. Thus, user-level thread is better than kernel level thread.
In both kernel and User level they have one stack per thread
Kernel level threads take a longer time to context switch since OS will have to save and reload each and every TCB (Thread Control block) where as in user level no kernel intervention threads simply context switch more efficiently. But there are disadvantages such as since OS sees the user leve threads as a whole process it will not give a large portion of CPU time for execution if a thread is blocked the whole process goes to the waiting state please correct my answer if im wrong godlovesu49@hotmail.com thanks regards yo
User-level threads have the advantage of being lightweight and can be managed without kernel intervention, allowing for faster thread switching. However, they are limited in their ability to utilize multiple processors efficiently and can be blocked by system calls made by a single thread. Kernel-level threads, on the other hand, offer better performance on multi-core systems and can take advantage of kernel features, but they are heavier in terms of resource consumption and switching between threads can be slower due to kernel involvement.
A multithreaded system comprising of multiple user-levelthreads cannot make use of the different processors in a multiprocessorsystem simultaneously. The operating system sees only a single processand will not schedule the different threads of the process on separateprocessors. Consequently, there is no performance benefit associatedwith executing multiple user-level threads on a multiprocessor system.
A kernel thread, sometimes called a LWP (Lightweight Process) is created and scheduled by the kernel. Kernel threads are often more expensive to create than user threads and the system calls to directly create kernel threads are very platform specific. A user thread is normally created by a threading library and scheduling is managed by the threading library itself (Which runs in user mode). All user threads belong to process that created them. The advantage of user threads is that they are portable. The major difference can be seen when using multiprocessor systems, user threads completely managed by the threading library can't be ran in parallel on the different CPUs, although this means they will run fine on uniprocessor systems. Since kernel threads use the kernel scheduler, different kernel threads can run on different CPUs. Many systems implement threading differently, A many-to-one threading model maps many user processes directly to one kernel thread, the kernel thread can be thought of as the main process. A one-to-one threading model maps each user thread directly to one kernel thread, this model allows parallel processing on the multiprocessor systems. Each kernel thread can be thought of as a VP (Virtual Process) which is managed by the scheduler.
There are two main kinds of threads implementations: User-space threads and Kernel-supported threads. Mikaela
The most common thread representation used in programming is the "lightweight thread" or "user-level thread." These threads are managed by the user-level library instead of the operating system, allowing for more efficient context switching and lower overhead. However, in many modern applications, particularly those requiring heavy concurrency, "kernel-level threads" are also prevalent, as they benefit from direct integration with the operating system's scheduling and management capabilities.
threads are the light weight process or it is a part of the process which can execute simulteniously by sharing systm resources.... two types of thread 1.user level thread 2.kernel level thread