Process management (seven) - the state with the conversion process
Status of the process
The lifetime of a process can be divided into a group of states, which characterize the entire process. The value of the process control system configuration in a state PCB.
During the life of the process, a process with at least three basic states: execution state, wait state and ready state.
Execution state
Process single-CPU system, at any one time in the execution of only one state.
Ready
The process has been ready state other resources in addition to the CPU as long to get through the dispatch processor, it can immediately put into execution.
Some systems for efficient use of memory, the ready state is further divided into memory and external memory ready state ready state. But it also increases the system overhead and system complexity.
Memory Ready
Only process is in memory ready state after receiving processor can be put into immediate execution
External memory ready state
After the process is in a ready state of the external memory of memory only to become ready before they can be scheduled for execution
Blocking state
The process of waiting for an event to give up the processor enters a wait (blocked) state.
Blocking state is divided in accordance with the conditions
Wait states may be further divided according to the type of waiting for an event to a different sub-states, such as memory wait, wait for the device, and data files waiting awaited.
Benefits:
The advantage of this control system is simple, the process of discovery and corresponding wake up more easily.
Disadvantages:
But the system is set too many states will result in increased system parameters and status of the conversion process.
State conversion process
Conversion Conditions
1. The process of change processes reflect the state of the implementation process.
2. With the implementation of these states and external conditions of the process of change and transformation occur.
3. The process of converting the state in addition to the use of different control process, sometimes by means of the hardware trigger to complete.
Suspend operation
What is the pending operation
The process of being eliminated from the memory
Introducing reasons
1. The end user need
2. parent request
3. The load adjustment needs
4. Operating system required, a process of "hang" operator (process memory temporarily eliminated)
Suspend the process of state transition may occur
1. Activities stationary Ready → Ready
2 → blocking activity still blocked
3. Ready → activity still ready
4. → stationary blocking blocking activity.