Shulou(Shulou.com)06/01 Report--

Page jitter (fluctuation)

One of the worst cases in the process of page replacement is that the pages that have just been swapped out have to be swapped into main memory immediately, and the pages that have just been swapped in have to be swapped out of main memory immediately. This frequent page tuning action is called trembling, or fluctuation. If a process takes more time to change pages than to perform, then the process is fluctuating.

Frequent occurrence of missing page suffixes (tremors), the second reason is that the number of pages visited frequently by a process is higher than the number of physical page frames available. Virtual memory techniques can save more processes in memory to improve piecemeal effectiveness. In the fluctuation form, almost all the space of the main memory is occupied by the process block, and the disposal machine and operation bits and pieces can directly visit as many processes as possible. But if the governance is improper, most of the time of the disposal machine will be used for the communication block, that is, pleading for the operation of the page, rather than performing the instructions of the process, which will greatly reduce the effectiveness of bits and pieces.

Task set (resident set)

A task set (or resident set) is a collection of pages that the process will visit within a certain distance. Pages that are often used are in the task set, while pages that are not temporarily used are discarded from the task set. In order to avoid trembling in bits and pieces, it is necessary to choose the appropriate task set size.

The reason for the task set model is to let the operation track the task set of each process in bits and pieces and assign physical blocks larger than its task set to the process. If there are still leisure physical blocks, you can call another process to memory to add the number of multiprograms. If the sum of all task sets is added so as to exceed the total number of available physical blocks, the operation will pause a process, call up its page and assign its physical blocks to other processes to avoid trembling.

The accurate selection of the size of the task set will have a major impact on the application rate of memory and piecemeal throughput.

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