From: ahemavathy (ahemavathy_at_hotmail.com)
Date: Sat Feb 28 2004 - 19:34:29 PST
The paper's idea is to introduce a layer of abstraction between the hardware and the commodity Operating Systems. This abstraction will make possible to run several OS on the same machine, several copies of the same OS, etc. thus efficiently sharing several resources. The virtual layer virtualizes all resources (Memory, I/O Devices, Disk, Network devices) of the machine. Other advantages of virtual machines include fault containment and scalability. The virtual machines have their own challenges which include overheads due to virtualization, resource management, communication and sharing.
When the virtual machine's OS is running Disco puts the processor in Supervisor mode. The processor always traps to the monitor. Memory is virtualized by adding another layer of physical-machine address translations in the TLB. Actual memory management techniques include page replication and migration. Copy on Write mechanism allows sharing memory. Disco supports global disk cache and thus eliminating replication during communication between virtual machines.
I found the concept of the paper interesting but was disappointed with the actual implementation and the performance measurements. Although the authors mention they didn't have to modify the OS much, the fact is they did and that is kind of unrealistic. Also It took me a long time to read the paper, it doesn't hold the reader's attention for some reason and also it was a difficult paper.
This archive was generated by hypermail 2.1.6 : Sat Feb 28 2004 - 19:35:45 PST