note update

- os

Author: xy-241

content/OS/CPU/CPU Cache.md

@@ -6,17 +6,24 @@ Author Profile:
 tags:
   - OS
 Creation Date: 2023-07-14T20:41:40+08:00
-Last Date: 2024-01-11T23:21:39+08:00
+Last Date: 2024-03-18T19:04:56+08:00
 References: 
 ---
 ## Abstract
 ---
-- A *small-sized* type of volatile computer memory that provides *high-speed data access* to a [[CPU]]
+- A **small-sized** type of volatile computer memory that provides **high-speed data access** to a [[CPU]]. **10-100 times faster** than accessing accessing data from [[Main Memory]]
 
+## Cache Locality
+---
+![[cache_locality.gif]]
+- Also known as **Locality of Reference**
+- [[#Cache Line]] is transferred into [[CPU Cache]] when we obtain [[Instruction]] or [[Data]] from [[Main Memory]]
+- If we are retrieving the same data or surrounding data. For the [[CPU]], instead of going to Main Memory to retrieve. It can obtain directly from the CPU Cache which is much faster (**10-100 times faster**)
+</br>
+
+- This contributes greatly to performance since [[Process (进程)]] usually only accesses a small portion of the [[Memory Address]] space within a small time interval 
 
 
-## Terminologies
----
 ### Cache Line
 * Ranging from 32 to 128 [[Computer Data Representation#Byte]]
 * When the CPU fetches data into the cache, it brings in entire cache lines rather than individual bytes
@@ -29,10 +36,3 @@ References:
 - When the [[CPU]] requests data that is not found in the [[CPU Cache]]
 - It requires fetching the data from the slower [[Main Memory]], incurring a higher access time compared to a [[#Cache Hit]]
 
-### Cache Locality
-- Also known as *Locality of Reference*
-- [[#Cache Line]] is transferred into [[CPU Cache]] when we obtain [[Instruction]] or [[Data]] from [[Main Memory]]
-- If we are retrieving the same data or surrounding data. For the [[CPU]], it instead of going to Main Memory to retrieve. We can obtain directly from the [[CPU Cache]] which is much faster
-</br>
-
-- [[Process (进程)]] accesses only a small portion of the [[Memory Address]] space within a small time interval 

content/OS/CPU/assets/cache_locality.gif

@@ -9,7 +9,7 @@ tags:
   - java
   - cpp
 Creation Date: 2024-01-13, 21:20
-Last Date: 2024-01-22T15:45:33+08:00
+Last Date: 2024-03-18T11:47:06+08:00
 References: 
 draft: 
 ---
@@ -24,10 +24,9 @@ draft:
 </br>
 
 ### Poor Memory Safety
-- [[Segmentation Fault]]
-- Malicious input to trick the program from doing unwanted things. [70% of reported security vulnerabilities](https://msrc.microsoft.com/blog/2019/07/a-proactive-approach-to-more-secure-code/) in low-level systems are caused by memory corruption. [Memory Safe Languages in Android 13 reduces vulnerabilities](https://security.googleblog.com/2022/12/memory-safe-languages-in-android-13.html)
-- Backdoor that some hackers are taking advantages of 
-- And many other [memory errors](https://en.wikipedia.org/wiki/Memory_safety#Types_of_memory_errors)
+- [[Segmentation Fault]] that leads to a crash in the [[Process (进程)]] or **write into other parts of the process**
+- When hackers can write into other parts of the process, they can use malicious input to trick the program from doing unwanted things. [70% of reported security vulnerabilities](https://msrc.microsoft.com/blog/2019/07/a-proactive-approach-to-more-secure-code/) in low-level systems are caused by memory corruption. [Memory Safe Languages in Android 13 reduces vulnerabilities](https://security.googleblog.com/2022/12/memory-safe-languages-in-android-13.html)
+- Backdoor that some hackers are taking advantages of, and many other [memory errors](https://en.wikipedia.org/wiki/Memory_safety#Types_of_memory_errors)
 
 ### Achieve Memory Safety
 **Rust**

content/OS/Memory/Memory Safety.md

@@ -3,7 +3,8 @@ Author:
   - Xinyang YU
 Author Profile:
   - https://linkedin.com/in/xinyang-yu
-tags: 
+tags:
+  - OS
 Creation Date: 2024-02-22, 17:53
 Last Date: 2024-02-22T18:10:51+08:00
 References: 

content/OS/Synchronization/Concurrency (并发).md

@@ -8,17 +8,24 @@ tags:
   - rust
   - c
   - java
+  - go
 Creation Date: 2024-01-04, 14:55
-Last Date: 2024-03-17T18:36:02+08:00
+Last Date: 2024-03-18T19:30:12+08:00
 References: 
 draft: 
 ---
 ## Abstract
 ---
-- A variable whose value is [[Memory Address]]
+- A [[Datatype]] whose value is [[Memory Address]], and itself is located at a memory address too
+- In the diagram below shows some [[Go]] codes, we create a pointer `var p *int32` and perform [[#Pointer Dereference]] with `*p`
+![[pointer_example.png|600]]
 
+>[!bigbrain] Pass data by pointer
+> Pass data to functions by pointer is **memory-efficient**. The data we pass into a function is basically a [[Memory Address]] to access that block of data. If we pass data into functions without pointer. We need to create an entire duplicate of data and pass it to the functions. 
+> 
+> In [[Java]], data is passed to functions by pointer by default. However in [[Go]], we need to explicity specify the pointer datatype for the function input, then we can pass data by point!
 ### Pointee
-- The **actual data** that a pointer points-to inside the [[Address Space#Heap Segment]]
+- The **actual data** that a [[Pointer]] points-to inside the [[Address Space#Heap Segment]]
 
 ### Pointer Dereference
 - The process of accessing [[#Pointee]] of a [[Pointer]]
@@ -29,6 +36,7 @@ draft:
 - [[Pointer]] that doesn't point to any memory location, basically contains a invalid [[Memory Address]]
 - In [[C]], it is represented by `0` or `nullptr`
 - In [[Java]], it is represented by `null`, [[Datatype#Custom Datatype]] can be `null`
+- In [[Go]], it is represented with `nil`
 
 ## Void Pointer
 ---