CS261 Fall 2014: Quiz #1
45 points: 15 per question
This exam is closed notes, closed papers, closed interwebs, closed everything.
Please use whatever word processing software that you'd like
to write your answers, but please send me either plain text
(≤ 80 characters per line)
Answers should be emailed to: firstname.lastname@example.org.
Here are the papers we've read:
- Baumann: The Multikernel: A New OS Architecture for Scalable Multicore Systems
- Bugnion: Disco: running commodity operating systems on scalable multiprocessors
- Corbató: An Experimental Time-Sharing System
- Creasy: The Origin of the VM/370 Time-Sharing System
- Daley: Virtual Memory, Processes, and Sharing in MULTICS
- Dijkstra: The Structure of the "THE" Multiprogramming System
- Gamsa: Tornado: Maximizing Locality and Concurrency in a Shared Memory Multiprocessor
- Kilburn: One Level Storage System
- Kivity: OSv-Optimizing the Operating System for Virtual Machines
- Leidtke: On micro-kernel Construction
- Rashid: From RIG to Accent to Mach: The Evolution of a Network Operating System
- Waldspurger: Memory Resource Management in VMware ESX Server
- Historical Context
List the papers (by number and author) in as close to chronological
order as you can
(earliest paper first). That is, if you think that the alphabetical list
reflects their chronology, you would write 1(Baumann), 2(Bugnion), 3(Corbato),
4(Creasy), ... 12(Waldspurger).
Next, take that chronology and insert logical eras, providing a brief
(one line) description of the eras. For example:
Stoneage (people chiseled programs on stone): 1(Baumann), 2(Bugnion), 3(Corbato)
Bronze age (people wrote programs on pennies): 4(Creasy), 5(Daley), 6(Dijkstra)
Pre-industrial revolution (computers built computers in castles): 7(Gamsa), 8(Kilburn), 9(Kivity)
Modern day (people worshiped computers): 10(Leidtke), 11(Rashid), 12(Waldspurger)
If you can give rough time frames for each era, do so.
- Reducing memory consumption in virtual machine environments
Although they share an intellectual heritage and both identify memory
redundancy as a problem in virtual machine based environments, Disco and
VMware ESX take rather different approaches to addressing it.
Explain the different approaches the two systems take, citing any similarities,
and then offer a justification for why they have each have arrived at their
- Be an OS Architect
The Harvard CS department is building a new computer, the Freakishly
Fast Machine (FFM). We are about to embark upon development of an
operating system for the machine and we need to select an architecture
before doing so. Given the machine description below, select one
of the architectures that we've read about (monolithic kernel,
microkernel, multikernel, hypervisor with conventional OS, hypervisor
with lightweight library OS) and make a case that it is best suited
to our machine.
- The machine is circular
- In the center is a low-energy, Terahertz processor (we have solved
the energy and heat problems that most people believe are insurmountable).
- The processor is surrounded by rings of memory -- the first ring
holds 1 GB memory accessible in a single cycle from
the processor (think of this as a cache).
- The next ring holds 512 GB, the next 1 TB, the next 512 TB, and
the outermost ring 1 PB of memory.
- Access to memory grows by about a factor of 5 per ring:
(e.g., ring 2 is accessible in 5 cycles, ring 3 in 25, etc).
- This also holds true for ring to ring communication:
the processor in ring N can access memory in rings N+1/N-1 in 5 cycles,
N+2/N-2 in 25 cycles, etc.
- All rings other than ring 1 contain a processor per 128 GB of memory
(it's embedded on the memory chips).
- Processors in the rings can talk to processors
in other rings with the same delay as they can access memory.
- Processors within the same ring can read each other's memory in a single
- The busses connecting the main processor, memory, and the memory
processors have infinite bandwidth.
- The machine will be networked with other machines of its type as well as
more conventional machines.
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