From: David V. Winkler (dwinkler_at_windows.microsoft.com)
Date: Mon Mar 01 2004 - 18:16:13 PST
Review: Disco: Running Commodity Operating Systems on Scalable Multiprocessors.
I liked this paper. The paper described the attempt to make a large multiprocessor machine look like many commodity machines. While the question of why one would want to do this remained largely unanswered, it is still an interesting problem.
The Disco operating system virtualizes the I/O, memory, and disks of the underlying machine. It does this in a fasion that makes the operating system work (largely) unmolested from shipping bits. While they did run into some difficulty with some of the MIPS instructions that couldn't be virtualized, this for the most part worked. The authors claim that this is isolated to the MIPS architecture.
Significant pain was involved in getting the memory mapping to work right. DMA provided a headache, but also provided the opportunity for use of copy-on-write for something other than fork, as this allows multiple reads from disk to be shared among virtual machines. However this can't be used for the isolation data.
Modifications of the operating systems was necessary for performance.
The performance numbers seem a bit shaky.
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