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Install K8S on VM and spring boot integration.

Installation Environment Vmware Workstation pro  It is recommended to use the  snapshot  to store the state of each installation stage to avoid installation failures and causing the installation to start from scratch. Ubuntu 22.04 windows 11 Hardware settings  create 3 VM: 4 cores and 4G memory and 100G capacity Before installing K8s (All use the root user) set host: 192.168.47.135 master 192.168.47.131 node1 192.168.47.132 node2 set root ssh connection: sudo su - echo "PermitRootLogin yes" >> /etc/ssh/sshd_config systemctl restart sshd sudo passwd ssh-keygen for i in {master,node1,node2}; do  ssh-copy-id root@$i; done set Ipvs and conf  create conf file: for i in {master,node1,node2}; do ssh root@$i 'cat << EOF > /etc/modules-load.d/containerd.conf overlay br_netfilter EOF'; done execute conf: for i in {master,node1,node2}; do ssh root@$i 'modprobe overlay;modprobe br_netfilter;'; done create 99-kubernetes-cri.conf file: for i in {maste...
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Virtual memory

Virtual memory

Separation of user logical memory from physical memory.

  • To run an extremely large process.
    • Logical address space can be much larger than physical address space.
  • To increase CPU/resource utilization.
    • A higher degree of multiprogramming degree.
  • To simplify programming tasks.
    • A free programmer from memory limitation.
  • To run programs faster.
    • Less I/O would be needed to load or swap.

Process & virtual memory

  • Demand paging: only bring in the page containing the first instruction.
  • Copy-on-write: the parent and the child process share the same frames initially, and frame-copy. when a page is written.
    • Allow both the parent and the child process to share the same frames in memory.
    • If either process modifies a frame, only then a frame is copied.
    • COW allows efficient process creation(e.g., fork()).
    • Free frames are allocated from a pool of zeroed-out frames(for security reasons).
      • The content of the frame is erased to 0
  • Memory-Mapped File: map a file into the virtual address space to bypass file system calls(e.g., read(), write())

Page Replacement Concept

  • When a page fault occurs with no free frame
    • Swap out a process, freeing all its frames, or
    • Page replacement: find one currently used and free it
      • Use dirty bit to reduce the overhead of page transfers-only modified pages are written to disk
  • Solve two major problems for demand paging
    • Frame-allocation algorithm:
      • Determine how many frames are to be allocated to a process.
    • Page-replacement algorithm:
      • Select which frame to be replaced
      • Goal: lowest page-fault rate
      • Evolution: running against a string of memory references (reference string) and computing the number of page faults
      • Replacement algorithms:
        • FIFO algorithm.
        • Optimal(Belady) algorithm.
        • LRU algorithm.
      • Counting algorithms:
        • LFU Algorithm(least frequently used).
        • MGU Algorithm(most frequently used).

Thrashing

  • If a process does not have "enough" frames.
    • The process does not have #frames it needs to support pages in active use. -> very high paging activity
  • A process is thrashing if it is spending more time.
  • To prevent thrashing, one must provide enough frames for each process:
    • Working-set model, page-fault frequency
reference:
https://www.amazon.com/-/zh_TW/Operating-System-Concepts-Abraham-Silberschatz/dp/1119800366/ref=sr_1_1?keywords=Operating-System-Concepts&qid=1669538704&s=books&sr=1-1

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GC Basic Algorithm

Theory Most GCs follow the theory of generational collection, which is based on the following two: Week generational hypothesis:  Most of the objects are short-living. Strong generational hypothesis:  The more times an object survives GC, the harder it is to die. Mark-Sweep After the marking phase has been completed all space occupied by unvisited objects is considered free and can thus be reused to allocate new objects. There may exist plenty of free regions but if no single region is large enough to accommodate the allocation, the allocation is still going to fail. Mark-Copy To avoid excessive fragmentation, it splits the space into two parts and copies the surviving objects into empty parts. The disadvantage is the need for one more memory region, which should be large enough to accommodate survived objects. Mark-Compact Like mark-copy, it doesn't require another space to copy but a more complex operation to move the object. Reachability analysis First, GC defines some spe...
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OS basic

Table of contents [ hide ] OS architecture The operating system architecture consists of three parts, user mode, kernel mode, and hardware. User mode is for the application to execute the user's program. Kernel mode is to control all the I/O devices and system stability. Storage device hierarchy System call The system call is a kind of software interrupt, including six categories. Process control. File management. Device management. Information maintenance. Communication. Protection. System calls use three methods to pass parameters. Registers. The table in memory. Push onto the stack. A view of operating system services reference: https://www.amazon.com/-/zh_TW/Operating-System-Concepts-Abraham-Silberschatz/dp/1119800366/ref=sr_1_1?keywords=Operating-System-Concepts&qid=1669538704&s=books&sr=1-1
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IOC and AOP

Table of contents [ hide ] The famous two features of Spring are IOC and AOP. Inversion of Control It uses the Spring's container to help us get objects, and the Spring manages these objects. There are two main types: Dependency Lookup: The Inversion of Control is limited to the container invoking callback methods that the application code can use to obtain resources. Dependency Injection:  The container is wholly responsible for wiring up components, and passing resolved objects into JavaBean properties or constructors for application. Aspect-Oriented Programming It helps to add new business logic across different modules without modifying the current code. reference: https://zhuanlan.zhihu.com/p/136474190 https://www.jianshu.com/p/7a1c0bad2708
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