From: Prasanna Kumar Jayapal (prasak_at_winse.microsoft.com)
Date: Mon Mar 01 2004 - 17:52:49 PST
This paper (Scale and Performance in the Denali Isolation Kernel) talks
about the design and implementation of a virtualization layer that
supports the execution of un-trusted internet services on a shared
infrastructure.
Denali emphasizes the configuration of one application per VM, and goes
further by reducing the role and capability of the operating system that
is sandwiched in-between. Standard operating systems cannot be run on
top of Denali, only simplified sub-operating systems may run. In
addition, the authors considered only independent applications that did
not require sharing amongst each other. This is a primary difference
when compared to the other VM paper, Disco that addresses sharing and
resource management among different applications.
The instruction set architecture of Denali is very similar to x86, but
only contains a subset of it. It hides the non-virtualizable aspects for
simplicity. However, it introduces couple new virtual instructions and
some virtual registers. These registers expose system information and
also serve as a sharing mechanism. Isolation kernel implements the
virtual architecture and multiplexes physical resources across
competeing VMs. It defines the size and the range of a VM, when it is
instantiated. I/O devices has exposed as virtual devices which are
similar in functionality to their physical counterparts but expose a
simpler interface. CPU multiplexing consists of two policies - a "gate
keeper policy" which enforces control, by choosing subset of active
machines and the "scheduler policy" which controls context switching.
The evaluation section was nice to read through and it kind of convinces
that the performance overhead of virtualization is reasonable.
Overall this was an interesting paper and I am really curious to see how
well the web servers, search engines and the content management systems
adopt to this technique.
This archive was generated by hypermail 2.1.6 : Mon Mar 01 2004 - 17:52:42 PST