Blocking on I/O
A thread can also enter the waiting state as the result of performing an input/output operation. I/O operations, such as disk writes or socket reads, are slow when compared to the execution speed of a CPU. While one thread waits for an I/O operation to complete, it is possible for other threads to perform quite a bit of processing. This is illustrated in Figure 8.3. When a thread performs an I/O operation, it enters the waiting state, where it remains until the I/O operation is completed. The thread is said to be blocked on I/O or blocking on I/O. When the I/O operation is completed, the thread transitions to the ready state.
Figure 8.3. Blocking on I/O.
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