考虑以下关于用户级线程和内核支持的线程的陈述
i. context switch is faster with kernel-supported threads
ii. for user-level threads, a system call can block the
entire process
iii. Kernel supported threads can be scheduled independently
iv. User level threads are transparent to the kernel以上哪些说法是正确的?
仅 (A) (ii)、(iii) 和 (iv)
(B) (ii) 和 (iii) 仅
(C) (i) 和 (iii) 仅
(D) (i) 和 (ii) 仅答案：(一)
解释：
| User level thread | Kernel level thread |
|---|---|
| User thread are implemented by users. | kernel threads are implemented by OS. |
| OS doesn’t recognized user level threads. | Kernel threads are recognized by OS. |
| Implementation of User threads is easy. | Implementation of Kernel thread is complicated. |
| Context switch time is less. | Context switch time is more. |
| Context switch requires no hardware support. | Hardware support is needed. |
| If one user level thread perform blocking operation then entire process will be blocked. | If one kernel thread perform blocking operation then another thread can continue execution. |
| Example : Java thread, POSIX threads. | Example : Window Solaris. |
http://en.wikipedia.org/wiki/Thread_%28computer_science%29
https://www.geeksforgeeks.org/difference-between-user-level-thread-and-kernel-level-thread/
这个问题的测验