preview

Case Study On Chimera

Better Essays

2.1 Multitasking Real Time Kernel Chimera Kernel differs from conventional operating systems since they provide constructs to control process execution as a function of time (real time kernel). The kernel provides task and memory management, flexible scheduling, user-space system calls to reduce operating system overhead, virtual timers, and a variety of communication and synchronization mechanisms. Chimera was intended to adopt most of the features of a multi-tasking operating system while keeping the response time low, a typical characteristic of a real time system. This was achieved by eliminating overhead features required of multi user operating systems like inter process security, large process space and virtual memory. It also provides …show more content…

Therefore features such as hardware caching or data dependency optimizations to increase average performance are undesirable in Chimera. Further, inter-process security is also given up to reduce system overheads in performing system calls as all the processes running on a single CPU are meant to be invoked by a single user and processes have equal privileges. Since real time programs are short repetitive operations with minimum dataset and instructions, virtual memory is not required thus eliminating memory management overhead from process context switch operations. 2.3 Deadline Based Scheduling RTOS must provide a priority mechanism that allows high-priority interrupts to take precedence over less important ones. Chimera implements Maximum Urgency First (MUF) scheduling algorithm which is a combination of fixed and dynamic priority scheduling. The fixed priorities are criticality and user priority. Criticality set to high or low determines if the task is critical to finish within the deadline. The dynamic priority, minimum laxity priority is an inverse of laxity defined as laxity = deadline_time – current_time – …show more content…

Therefore all classes of design (architectural, procedural and data design) become more complex. Predictability of a real time operating system puts performance at stake. However in Chimera high performance features make it different from other RTOSs. Distributed operating systems pose a serious issue of security and therefore need to incorporate Authorization and Authentication mechanisms. Many of the information resources that are made available and maintained in distributed systems have a high intrinsic value to their users. Their security is therefore of considerable importance. Sufficient information regarding this aspect is not available for

Get Access