The number of active processor
Computer memory is organized in at least2 levels: main memory, expensive queue system process but very fast and secondary memory, cheaper but slower. An important task for memory management is the organization of memory on two levels. One of the main operations for the operating system is bringing programs in main memory to be executed by the processor. In modern systems it is known as virtual memory. Virtual memory is based on one system queuing management of the following techniques of organization: segmentation and paging. If partitions of equal size (fixed partitioning) process can be loaded in a specific partition if its size is less than or equal to the size of the partition.
If all partitions are full swap process can be. If a program can not enter a partition this must be indicated. Basically, the system is not effective as a program how small will occupy an entire portative lead to internal fragmentation. Figure 4. 2. Avem2 system queuing management examples for secure partitioning. The first presents partition of equal size while the second partition has different sized partitions that compose it. Secure partitioning process has many shortcomings. Because fixed partitions does not matter which one is used. If we partition sizes there are 2 ways of awarding processes. The simplest method is to assign each process of the smallest partition in which it enters. There is a queue for each partition at a time because it is possible that several processes similar dimension to want the same partition.
The advantages are that it minimized the amount of wasted memory. But this way is system queuing management optimal in terms of a partition but not in terms of the whole system. In the next picture we see cele 2 mechanisms are discussed. Assuming that at some point a de 8 megabytes memory area is not occupied by any process but there are queues for memory in smaller realize that this first mechanism can lead to various delays that could be avoided if s it allows a process to use less memory and larger areas. Thus, we have a second approach with a single queue for all processes. A process will be chosen for the smallest partition which he can cups.
Disney world's management of waiting lines
In if all partitions are occupied when a decision will be taken swap are. In this case, the various factors can be taken as priority or other criteria. Partitioning by this method provides a relative flexibility but there are a number of disadvantages: the number of partitions limit the number of active system queuing management processes in the system; partitions occupation is not effective. Today this type of organization is no longer used, only part of the history of computers and operating systems. In the dynamic partitioning, partitions are of variable length and number. Each process has allocated exactly as much memory as it needs.
The image below initial main memory is empty except for the part occupied by the operating system. The first three processes are loaded starting location they complete operating system and occupies just enough space for each process. Then make a swap os processes la2 leaving enough room for others because at that time no process is in a state of ready. Since procesul4 as employment is lower in memory than procesul2 there is a free space in memory.