The process of moving required memory pages back from swap to RAM in known as page in.įollowing figure illustrates this process The process of moving idle memory pages from RAM to swap is known as page out.
This way by using same physical memory Linux can run more processes with swap space. Vice versa when process B is executing, memory pages occupied by process A will be moved in swap space.
If swap space is configured and RAM is filled, idle pages will be moved in swap space.įor example, when process A is executing, memory pages occupied by process B will be moved in swap space.
Swap space can improve this situation a little bit. System will not start new process until any existing process is finished. Following figure illustrates this scenario.Īs we can see in above figure, no memory pages available for another process. Both processes are assigned memory pages. This process continues until the jobįinishes and needs no more time on the CPU. Once the other jobs have had theirĮqual share (100 ms each), job1 will get another allocation of CPU time and the cycle will repeat. The round-robin scheduler will suspend the job after 100 ms and give other jobs their time on the CPU. For example, if the time slot is 100 milliseconds, and job1 takes a total time of 250 ms to complete, If process is not finished in allowed time slot then it will be terminated and resumed next time when this Further each process is assigned a quantum In round-robin fashion, all processes are scheduled in a queue based on time sharing technique. CPU processes services or applications in round-robin fashion. Memory pages are assigned to service or process running in CPU. System divides RAM in smaller chunks known as memory pages. The swap space is the space of hard disk that can be used as the memory. Linux uses swap space to deal with the shortage of physical memory. Any service may use more memory in its peak time. This kind of memory spike is very common in server system. For example a university website which is hosted in Linux server system may consume more memory on the day when exam result is announced. Sometime some process may use more than expected memory. Server systems are built to process several processes simultaneously. Traditionally Linux was developed for server system.
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