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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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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 specific objects as Garbage Collection Roots. Examples of such GC roots are:
  • Local variable and input parameters of the currently executing methods
  • Active threads
  • Static field of the loaded classes
  • JNI references
Next, GC traverses the whole object graph in your memory, starting from those Garbage Collection Roots and following references from the roots to other objects, e.g. instance fields. Every object the GC visits is marked as alive.

When the marking phase finishes, every live object is marked. All other objects are thus unreachable from the GC roots, implying that your application cannot use the unreachable objects anymore. Such objects are considered garbage and GC should get rid of them.



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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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Cpu scheduling

Table of contents [ hide ] Basic concept The idea of multiprogramming: Keep several processes in memory. Every time one process has to wait, another process takes over the use of the CPU. CPU-I/O burst cycle: Process execution consists of a cycle of CPU execution and I/O wait(i.e., CPU burst and I/O burst). Generally, there is a large number of short CPU bursts and a small number of long CPU bursts An I/O-bound program would typically have many very short CPU bursts. A CPU-bound program might have a few long CPU bursts. CPU scheduler Select from the ready queue to execute(I.e allocates an APU for the selected process) CPU scheduling  decision may take place when a process: Switch from running to waiting state. Switch from running to ready state. Switch from waiting to ready. Terminates. Non-preemptive scheduling: Scheduling under 1 and 4(no choice in terms of scheduling). The process keeps the CPU until it is terminated or switched to the waiting state. Preemptive schedul...
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Process

Table of contents [ hide ] A process is a program that is executed in memory. Process layout A process includes: Code segment. Data section-global variables. Stack-temporary local variables and functions. Heap-dynamic allocated variables or classes. Current activity(program counter, register contents). A set of associated resources. Process status Process control block A process control block (PCB) is the kernel data structure that represents a process in an operating system.   Context switch means the kernel saves the state of the old process and loads the saved state for the new process. Process state. Program counter. Cpu register. Cou scheduling. Memory-management information. I/O status information. Accounting information. Process Schedulers Short-term(CPU scheduler) Selects which process should be executed and allocated CPU(ready state -> run state). Long-term(job scheduler) Selects which processes should be loaded into memory and brought into the ready queue(ne...
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