The borrowed virtual time BVT scheduling algorithm is described in 11 The

The borrowed virtual time bvt scheduling algorithm is

This preview shows page 5 - 6 out of 7 pages.

The borrowed virtual time (BVT) scheduling algorithm is described in [11]. The essential of this algorithm is fair-share scheduler based on the concept of virtual time, dispatching the runnable virtual machine (VM) with the smallest virtual time first. Moreover, the algorithm provides low-latency support for real-time and interactive applications by allowing latency sensitive clients to “warp” back in virtual time to gain scheduling priority. The client effectively “borrows” virtual time from its future CPU allocation. The Simple Earliest Deadline First (SEDF) scheduling algorithm is presented in [12]. In this algorithm, each domain specifies its CPU requirements. After all runnable domains receive their CPU share, SEDF will distribute this slack time fairly manner. In fact, the time granularity in the definition of the period impacts scheduler fairness. The Credit Scheduling algorithm is described in [13]. It is Xen’s latest proportional share scheduler featuring automatic load balancing of virtual CPUs across physical CPUs on an SMP host. Before a CPU goes idle, it will consider other CPUs in order to find any runnable virtual CPU (VCPU). This approach guarantees that no CPU idles when there is runnable work in the system. In [14], the authors present a novel virtual I/O scheduler (VIOS) that provides absolute performance virtualization by being fair in sharing I/O system resources among operating systems and their applications, and provides performance isolation in the face of variations in the characteristics of I/O streams. In the scheduler, the VIOS controls the coarse- grain allocation of disk time to the different operating system instances and the output scheduler may determine the fine- grain interleaving of requests from the corresponding operating systems to the storage system. D. Security In a virtual machine system, the computer that is being virtualized is vulnerable to all the traditional attacks and exploits that are common to the normal environment. Therefore, the security expectations are higher in the virtual machine system than that in normal environment. Moreover, there are possible points of entry, more holes to patch and more interconnection points in the virtual machine system. In order to ensure the security of virtual machine system, some security mechanisms and methods are presented. These security mechanisms and methods can be described as follows. An experience of use of virtual machines for the security of systems was described in [15]. In the paper, Revirt is defined as an intermediate layer between the monitor and the host system, and the captured data is sent to the host system through the syslog process (the standard UNIX logging daemon) of the virtual machine. However, if the virtual system is compromised, the log messages can be manipulated by the invader and consequently are no more reliable. A VMI-IDS (Virtual Machine Introspection Intrusion Detection System) is described for searching intrusion evidences in [16]. In the system, the virtual machine executes directly on top of the hardware and the intrusion detection system executes in a privileged virtual machine and scans data extracted from the other VMs. The
Image of page 5
Image of page 6

You've reached the end of your free preview.

Want to read all 7 pages?

  • Fall '16
  • Sir Adnan
  • virtual machine

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors