What is the biggest advantage of implementing threads in user space? What is the biggest disadvantage?

The biggest advantage of implementing threads in user space is that it is faster and more efficient than kernel-level threads. User-level threads can be created and managed without the overhead of system calls, context switching, and other kernel-level operations.

The biggest disadvantage of implementing threads in user space is that they are not truly concurrent, as they are dependent on the scheduling of the underlying operating system. This can lead to issues with synchronization and resource sharing, as well as decreased performance in situations where there are many threads competing for resources. Additionally, user-level threads are not as well-suited for multi-processor systems, as they are not able to take full advantage of the available hardware.