Linux Process thread Awareness

• Process:

  • Minimum unit of resource allocation

  • An instance of a program, just like a class and an object.

  • The program has implemented a collection of data structures to a certain extent.

    
    

• Thread:

  • most of the expense is spent when the process is created, so the thread is lightweight

  • Minimum unit of program execution

  • Execution fluid of the process

  • Basic unit of CPU dispatch and dispatch

  • Resources for shared processes

  • Standalone operation

The process has a separate address space, and after a process crashes, it does not affect other processes in protected mode, and the thread is just a different execution path in a process. Thread has its own stack and local variables, but the thread does not have a separate address space, a thread dead is equal to the entire process to die, so the multi-process program is more robust than multi-threaded programs, but in the process of switching, the cost of large resources, efficiency is worse. But for some concurrent operations that require simultaneous and shared variables, only threads can be used, and processes cannot be used.

using multi-threaded is Span style= "Color:rgb (255,0,0);" > compared to the process, it is a very "frugal" multi-tasking mode of Operation . We know that under the Linux system, starting a new process must be assigned to its own address space, creating numerous data tables to maintain its code snippets, stack segments, and data segments, which is an "expensive" multi-tasking way of working. Instead, multiple

The second reason to use multithreading is the convenient communication mechanism between threads . For different processes, they have independent data space, it is not only time-consuming, but also inconvenient to transmit the data only by means of communication. Threads do not, because data space is shared between threads in the same process, so that the data of one thread can be used directly by other threads, which is not only fast, but also convenient. Of course, the sharing of data also brings some other problems, some variables can not be modified by two threads at the same time, some of the sub-programs declared as static data more likely to have a catastrophic attack on the multi-threaded program, these are the most important to write a multi-thread programming.

In addition to the advantages mentioned above, not compared with the process, multi-threaded procedure as a multi-tasking, concurrent work, of course, the following advantages:

• Improve application responsiveness. This is especially meaningful to the graphical interface program, when an operation takes a long time, the entire system waits for this operation, the program does not respond to the keyboard, mouse, menu operation, and the use of multi-threading technology, the time-consuming operation (consuming) into a new thread, can avoid this embarrassing situation.

• Make multi-CPU systems more efficient. The operating system guarantees that when the number of threads is not greater than the number of CPUs, different threads run on different CPUs.

• Improve the program structure. A long and complex process can be considered to be divided into multiple threads and become a separate or semi-independent part of the run, which facilitates understanding and modification.

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Linux Process thread Awareness