W4D1&W8D1&W12D1-Fengyueyang

W12D1/W12D1-Fengyueyang/W12-Fengyueyang.md

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+### Symmetric Multiprocessors
+
+![](image/6.png)
+
+##### Multiprocessor Synchronization
+
+![](image/7.png)
+
+![](image/8.png)
+
+### Distributed Shared Memory 
+
+![](image/1.png)
+
+**False Sharing.**
+
+![](image/2.png)
+
+### Distributed Systems 
+
+![](image/3.png)
+
+### Network Services
+
+![](image/4.png)
+
+### Network Services
+
+![](image/5.png)

W4D1/W4D1-Fengyueyang/W4D1-Fengyueyang.md

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+# W4D1
+
+## review
+
+Scheduler
+
+- Process/Thread Sched
+  - O(1) SD/RSDL, CFS
+  - Unix's Sched Principle
+- Higher/lower
+  - User-level
+  - I/O-level
+
+Q1: Perf (system) vs. Fairness (user)
+
+Q2: Timeslice vs. Priority
+
+Prio = static + nice + (CPU / 2) 
+
+## Memory Management
+
+### topic
+
+Process’s Memory Space vs. Kernel’s Mem Space (i.e mem_map_t)
+
+Example: Buddy System
+
+## Memory
+
+### Running Multiple Programs Without a Memory Abstraction
+
+![image-20230616214117718](image/image-20230616214117718.png)
+
+Illustration of the relocation problem.
+
+(a) A 16-KB program. 
+
+(b) Another 16-KB program. 
+
+(c) The two programs loaded consecutively into memory.
+
+### No Memory Abstraction
+
+![image-20230616214048430](image/image-20230616214048430.png)
+
+Three simple ways of organizing memory with an operating system and one user process. Other possibilities also exist
+
+
+
+### Memory Management with Bitmaps
+
+![image-20230616214309964](image/image-20230616214309964.png)
+
+(a) A part of memory with five processes and three holes. The tickmarks show the memory allocation units. The shaded regions (0 in the bitmap) are free. 
+
+(b) The corresponding bitmap. 
+
+(c) The same information as a list.
+
+### Base and Limit Registers
+
+![image-20230616214145227](image/image-20230616214145227.png)
+
+Base and limit registers can be used to give each process a separate address space.
+
+### Swapping
+
+![image-20230616214213241](image/image-20230616214213241.png)
+
+Memory allocation changes as processes come into memory and leave it.  The shaded regions are unused memory
+
+![image-20230616214234893](image/image-20230616214234893.png)
+
+(a) Allocating space for a growing data segment. 
+
+(b) Allocating space for a growing stack and a growing data segment.
+

W8D1/W8D1-Fengyueyang/W8-Fengyueyang.md

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+### The Security Environment Threats
+
+- Confidentiality
+- Integrity
+- Availability
+
+##### Trusted Computing Base
+
+![](image/1.png)
+
+##### Protection Domains
+
+![](image/2.png)
+
+##### Access Control Lists 
+
+![](image/3.png)
+
+##### Capabilities 
+
+![](image/4.png)
+
+### Multilevel SecurityBell-LaPadula Model
+
+Bell-LaPadula Model rules for information flow:
+
+- The simple security property
+  Process running at security level k can read only objects at its level or lower
+- The * property
+  Process running at security level k can write only objects at its level or higher
+
+![](image/5.png)
+
+### Digital Signatures
+
+![](image/6.png)
+
+### Authentication 
+
+Methods of authenticating users when they attempt to log in based on one of three general principles:
+
+- Something the user knows.
+- Something the user has.
+- Something the user is.
+
+#### Buffer Overflow Attacks
+
+![](image/7.png)