P4L3 - Distributed Shared Memory Flashcards
What is distributed shared memory?
A service that manages memory access across multiple nodes so that applications will have the illusion that they are running on a single shared-memory machine
In DSM, each node in the system owns some portion of ____ ____
physical memory
In DSM, each node needs to be involved in some _____ ______
consistency protocols
T/F: Overall memory access will be slower in a DSM environment
True, due to the network costs
What are the two ways in which DSM can be supported?
- Hardware
2. Software
What does hardware-supported DSM rely on?
physical interconnect
What is a downside of hardware-supported DSM?
Typically very expensive
What are some options for granularity of sharing with DSM?
- Variable Granularity
- Page Granularity
- Object Granularity
What is one side effect of increasing the granularity of sharing?
False Sharing
In the scope of DSM, describe the concept of false sharing
When different entities that may exist on the same memory page can trigger coherence mechanisms falsely. An example would be one process modifying a variable x and another modifying a variable y that happen to exist in the same page
In the scope of DSM, what is the simplest kind of application?
Single Reader/Single Writer since there are no consistency or sharing related challenges
For a DSM solution to be useful, it must provide what
Good performance to applications
What is the core performance metric for analyzing DSM performance?
Access latency
Describe the difference between migration and replication
Migration - whenever a process on another node needs to access remote state, copy the state over to that node
Replication - Copy state on multiple nodes
The node where a page is located is typically referred to as the ___ ____ for that page?
Home Node