CSE 221 Homework 3
Due: Tuesday, November 29, 2016 at the
start of class (8am)
Answer the following questions. For questions asking for short
answers, there may not necessarily be a "right" answer, although some
answers may be more compelling and/or much easier to justify. But I
am interested in your explanation as much as the answer itself. Also,
do not use shorthand: write your answers using complete sentences.
- The Scheduler Activations paper states that deadlock is
potentially an issue when activations perform an upcall:
"One issue we have not yet addressed is that a user-level thread could
be executing in a critical section at the instant when it is blocked
or preempted...[a] possible ill effect ... [is] deadlock (e.g., the
preempted thread could be holding a lock on the user-level thread
ready list; if so, deadlock would occur if the upcall attempted to
place the preempted thread onto the ready list)." (p. 102)
Why is this not a concern with standard kernel threads, i.e., why
do scheduler activations have to worry about this deadlock issue, but
standard kernel threads implementations do not have to?
- The IX system design is tailored to data center services that
have short messages and short service times (i.e., per request, very
little CPU time is spent in the application). The paper motivates IX
with other applications (e.g., a Web server), but evaluates only
- If instead requests spent a significant amount of CPU time in the
application — 3x the time the request would spend in the
networking stack on a normal Linux OS — would IX still be a good
system to use? Explain why or why not.
- If instead every request initiated an I/O to disk, would IX still
be a good system to use? Explain why or why not.
- The FFS, LFS, and Soft Updates file systems introduced new
designs and optimizations to improve upon a previous file system
implementation. Consider the following three changes in underlying
workload and storage technology. For each of the three file systems,
explain whether the improvements they found with their design and
optimizations would still hold under each of these changes. For
instance, would FFS still see similar improvements relative to the old
Unix file system under a read-dominated workload?
- Read-dominated workload (100x reads per write)
- Latency improves by 10x, bandwidth improves by 10x ("SSD")
- Latency degrades by 10x, bandwidth degrades by 10x ("Internet Cloud
Last updated: 2017-07-27 15:52:13 -0700