DistOS 2023W 2023-01-25 - Revision history

Soma at 02:08, 26 January 2023

2023-01-26T02:08:55Z

← Older revision		Revision as of 02:08, 26 January 2023
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	* How similar are modern multi-core systems to networked DSM implementations? How are they different?		* How similar are modern multi-core systems to networked DSM implementations? How are they different?
	* What is unclear or confusing about DSM & the readings?		* What is unclear or confusing about DSM & the readings?

			==Notes==

			<pre>
			Lecture 6
			---------

			Group reports
			- make sure they are more like meeting minutes, not just
			summaries of the readings
			- mention points of confusion, conflicts, questions, in addition to
			what was in the readings
			- don't need to name names to protect the guilty
			- explain the concepts then that are mentioned so the document has utility
			afterwards (say when studying for the midterm and final)
			- can use bullet points, but they should be wordy bullet points

			Discussion questions

			What is the dream of DSM?
			- make a bunch of computers behave as if they have one shared pool of memory
			- doesn't matter where the memory is, it can all be used

			What makes DSM hard?
			- networking makes it possible, but...
			- the memory ISN'T shared, we're simulating sharing
			- and it is impossible to make the semantics completely identical
			to shared memory without killing performance
			- because at the end of the day, each CPU can only access data that is in its own RAM
			- (so we're always making copies)

			Why can't we have a general solution to DSM?
			- in order to maximize performance, we have to fit the architecture to the code's access patterns
			- if access is perfectly random nothing will work
			- perfect locality - well, why did you bother with DSM
			- are we sharing data mostly read only? Or will we need concurrent writes?
			when are we doing each?


			Why are consistency models so important to DSM?
			- what sort of guarantees are we placing on the interactions?
			- how deterministic do we need things to be?
			- comes down to what happens when things happen "at the same time"
			- for correctness, we normally need a deterministic sequential
			model of execution
			- but for performance maybe we can relax this



			What is a coherence policy in DSM?
			- how do we do updates?
			- typically involves validation because it is fastest (you don't have a current copy, someone else does, if you need it go ask for it)

			Do you think we use DSM today? Why or why not?
			- we generally don't use DSM for sharing memory between multiple nodes/hosts
			- we'll just do the messaging ourselves, tends to be more efficient
			- HOWEVER, we do use them inside all multicore/multi processor systems!
			- this is how the distributed caches & cores all act like there is
			just one pool of RAM

			How similar are modern multi-core systems to networked DSM implementations? How are they different?
			- see above!


			Why are we talking about DSM here even though it isn't used at a large scale?
			- example of an idea that is very powerful and useful at a certain scale
			- however, it doesn't scale to larger systems and so we need different ideas

			What modern CPUs do to make multicore work is black magic, very tricky stuff
			- they really are distributed systems

			In fact, if you want modern multicore systems to perform best, you minimize the amount of shared memory that your application uses
			- communication is what kills the performance of all distributed applications,
			so you limit it as much as possible
			</pre>

Soma: /* Discussion Questions */

2023-01-25T16:33:00Z

Discussion Questions

← Older revision		Revision as of 16:33, 25 January 2023
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	* What is a coherence policy in DSM?		* What is a coherence policy in DSM?
	* Do you think we use DSM today? Why or why not?		* Do you think we use DSM today? Why or why not?
	* How similar are modern multi-core systems to networked DSM implementations?		* How similar are modern multi-core systems to networked DSM implementations? How are they different?
	* What is unclear or confusing about DSM & the readings?		* What is unclear or confusing about DSM & the readings?

Soma: /* Discussion Questions */

2023-01-25T16:32:49Z

Discussion Questions

← Older revision		Revision as of 16:32, 25 January 2023
Line 7:		Line 7:
	* What is a coherence policy in DSM?		* What is a coherence policy in DSM?
	* Do you think we use DSM today? Why or why not?		* Do you think we use DSM today? Why or why not?
			* How similar are modern multi-core systems to networked DSM implementations?
	* What is unclear or confusing about DSM & the readings?		* What is unclear or confusing about DSM & the readings?

Soma: /* Discussion Questions */

2023-01-25T16:31:44Z

Discussion Questions

← Older revision		Revision as of 16:31, 25 January 2023
Line 5:		Line 5:
	* Why can't we have a general solution to DSM?		* Why can't we have a general solution to DSM?
	* Why are consistency models so important to DSM?		* Why are consistency models so important to DSM?
			* What is a coherence policy in DSM?
	* Do you think we use DSM today? Why or why not?		* Do you think we use DSM today? Why or why not?
	* What is unclear or confusing about DSM & the readings?		* What is unclear or confusing about DSM & the readings?

Soma: /* Discussion Questions */

2023-01-25T16:31:06Z

Discussion Questions

← Older revision		Revision as of 16:31, 25 January 2023
Line 4:		Line 4:
	* What makes DSM hard?		* What makes DSM hard?
	* Why can't we have a general solution to DSM?		* Why can't we have a general solution to DSM?
			* Why are consistency models so important to DSM?
	* Do you think we use DSM today? Why or why not?		* Do you think we use DSM today? Why or why not?
	* What is unclear or confusing about DSM & the readings?		* What is unclear or confusing about DSM & the readings?

Soma: Created page with "==Discussion Questions== * What is the dream of DSM? * What makes DSM hard? * Why can't we have a general solution to DSM? * Do you think we use DSM today? Why or why not? * What is unclear or confusing about DSM & the readings?"

2023-01-25T16:30:31Z

Created page with "==Discussion Questions== * What is the dream of DSM? * What makes DSM hard? * Why can't we have a general solution to DSM? * Do you think we use DSM today? Why or why not? * What is unclear or confusing about DSM & the readings?"

New page

==Discussion Questions==

* What is the dream of DSM?
* What makes DSM hard?
* Why can't we have a general solution to DSM?
* Do you think we use DSM today? Why or why not?
* What is unclear or confusing about DSM & the readings?