Project1_VFS - CIS657PrinciplesofOperatingSystems Project...

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CIS 657 Principles of Operating Systems Project 1: Fair Share Scheduling for FreeBSD 5.2 Milestone I : 10/13 Thu II : 10/20 Thu Submission: 10/24 Mon 1. Introduction This is an individual project. You may not pair up, give, receive, share or discuss  the  concepts, designs, programs, or any other part of your work. Both 4.4 BSD scheduler and ULE scheduler prioritize I/O-bound interactive processes over CPU- bound "noninteractive" processes. When OS uses a threshold or cutoff for a binary decision, the user may notice a change in  behavior   as   a   process   crosses   the   boundary.   For   example,   after   a   very   small   change   in  interactivity score, ULE may delay scheduling a process significantly, by placing it in the next  (rather than current) queue. In this project  you  will  implement  a version of  Fair Share  (FS) scheduler  that resembles  "Completely   Fair   Share   (CFS)"   scheduling   Linux   uses   (since   June   2008).   FS   does   not  categorize/classify, so there is no sudden change in behavior. 2. Very Fair Scheduler (VFS) As "Completely" in CFS is not entirely true, and we won't fully implement CFS, we'll call this  "Very Fair Scheduling" (VFS). Our VFS falls somewhere between user and process based fair  share scheduling methods, and CFS (but could also be considered to be either one). In VFS, you  need to first divide CPU access evenly across users, and then also divide evenly between  processes of the same user. For example, if user A has 2 processes and user B has 10 processes runnable, fair share for user  A's processes is 25% of CPU time each, whereas fair share for user B's processes is 5% of CPU  time each. We only care about runnable processes. VFS makes sure that no user and no process will ever starve / be forgotten. Note that, even  though VFS tries to split CPU time evenly, some processes just sleep for long periods and will not  catch up (but will still be given all the time to catch up). VFS can be implemented quite simply,  without heuristics, categories (like interactive, noninteractive), decision making or binning. The  process farthest behind in having a proportional fair share is the one to schedule. For this project, I would like you to ignore multiple CPU / multiple core cases; we'll only run tests 
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This note was uploaded on 10/19/2011 for the course CIS 657 taught by Professor Chapin,s during the Fall '08 term at Syracuse.

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Project1_VFS - CIS657PrinciplesofOperatingSystems Project...

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