[MSYS 51] Module 2.3 - Process Management, Multitasking, and Virtualization

Process

Informal

• A program in execution (currently running)

More broadly

• All CPU activities (user programs, internal OS tasks, etc.)

Process Control Block

• Record per process

• Starts when process executes

• Purged when process exited

• Information kept in the Process Control block (PCB)

  • Created when a process / application is executed

• Typical data in PCB include:

  • Process ID (PID)

    • Similar to PK

  • Process state

  • Process priority (diff per process)

  • Memory usage

  • Assigned resources

Resources Needed: CPU (Central Processing Unit)

• During execution

  • every process needs a computing core exclusively

• Scheduling needed due to limited number

  • shared by time, each process is a queue

• Responsible for executing instructions and performing calculations

• Processes data and coordinates tasks between hardware and software components

Resources Needed: Main Memory

• Loaded from secondary storage

• Shared in space, loc diff

• Computing core: shared in time ; each computing core is mutually exclusive -> one process in each computing core

• where it is stored; keeping track of loc in MM

Resources Needed: I/O

• User interaction, file access

• Which i/o devices it needs to execute

Sample Process List

Threads

• Parts of a process that execute simultaneously

  • May run concurrently

• AKA lightweight process (synonymous) 

  • THREAD LEVEL

    • It’s a process that manages the threads

    • Threads - parts of a process

    • Thread = “lightweight process”

      • Multiple lightweight processes in a process

      • Multithreaded process if madaming thread ≠ heavyweight

      • Synchronization for dependencies -> iba ung outcome depende sa arrangement ng thread

        • Challenge: regardless of the sequence of indiv threads, the outcome should ALWAYS be the same

• A heavyweight process contains ONE THREAD

• Peer threads

  • from same process

  • share resources, data

• Process dependent

Multiple Threads Scenario

IF multiple threads

• Process 1 has 3 lightweight process (T1,T2,T3) != heavyweight process

  • A multithreaded process

  • Not a heavyweight because it has multiple threads

  • EACH ONE is a lightweight process

    • Kasi yung thread is synonymous with lightweight process

    • Magkaibang context

• Process 2 only contains T1 = heavyweight proces

• P2 is composed on multiple lightweight processes (FALSE) 

• P1 is a heavyweight process (FALSE)

• CANNOT say that a process is lightweight, process can be heavyweight

  • Lightweight process = thread

    • Does not refer to the no. of threads in a process

    • HINDI PWEDE na a process w/ multiple threads = lightweight process

TLDR Threads

Key Definitions:

✅ Process – An independent execution unit with its own memory space.
✅ Thread – A smaller execution unit within a process that shares the process’s resources (like memory, files, etc.).
✅ Lightweight Process (LWP) – Another term for a thread in many OS concepts.

❌ Wrong Concept:

"A process with multiple threads is lightweight."
✅ Correct Concept:
"Threads are lightweight, but the process itself is independent of this classification."

💡 TL;DR:

• Thread = Lightweight Process ✅

• Process ≠ Lightweight Process (regardless of thread count) ✅

• More threads ≠ Lightweight Process ✅

Threads Pros & Cons

ADVANTAGES

• Efficiency

• Potentially faster process execution

DISADVANTAGES

• Synchronization complexities

• A misbehaving thread may cause problems to entire process

Resource hungry applications (games, ai, editing) - benefits from multithreading capabilities

Time Slicing

• Applies to a single core

• Processes share processor time

• Needs exclusive access to a CPU core to run

• Supported by modern CPUs

Processing power is a scare resource

• Kahit na 64 computing force

• You’re talking about 100 processes

• Time slicing is needed in modern-day computing

Each core is a mutually exclusive resource = time shared

• 1 process at any given core at any given time

For a quadcore cpu how many processes? 4

Computing Core Scenario

Running: P21 - which process among the ones in the queue will run next

• Which component uses that strategy to select the next process to run

  • OS - performs the selection

    • Within the Kernel

    • Software

    • CPU scheduler

• COMPUTING CORE

  • Current process assigned to core (time shared)

    • Remote buttons analogous to instruction set (all capabilities of CPU itself)

    • Job: determine who gets to use the remote next

    • w/o scheduler, no one knows who will go next

    • Process that’s assigned to the core SELECTS what’s next (software)

      • At the end of the process, may scheduler na (usually)

  • The core itself - hardware; can’t do anything without instructions

Inter-Process Communication

• A process may communicate with one or more processes

• Challenges (same as peer threads, but more complex)

  • Synchronization

  • Security

• E.x. Traditional relationship

• Within same machine

Inter-Process Communication over a Network

• More complicated than Inter-process

• Socket

  • An endpoint for communication

  • Facility for processes to communicate over a network

  • Analogy: phone, video conferencing (if LDR)

• A pair of communicating processes consists of two sockets

• SECURELY transferring information from one machine to another via network

• E.x. LDR

IP Address: Contact info of a specific process in that machine: 159.22.118.180

Virtualization

• Multiple virtual systems hosted in one hardware

• Illusion of separate systems

• Implemented via a hypervisor

• May be hardware-supported

• Hosting all of these in one hardware simultaneously

  • Windows, linux, macOS, Win60

• Multiboot machine -> OS is booted sa start palang (2 OS: dual boot)

  • Run OS until you shut it down

Virtualization Pros & Cons

Hypervisor

• Software that manages hardware

• Creates multiple virtual machines made available to each OS

• Similar to how an OS works

Kinda like emulators of games (playstation, nintendo) → creates VMs to run diff platforms

• Virtual Machine: emulation of hardware

  • Make use of emulation

  • Hardware is limited; Multiple OS spreads hardware thinly 

  • Quadcore - kaya pa 4 OS pero pag mas madami, hypervisor would have to timeslice

  • HV has to work with existing hardware

VM ware: popular provider

Before clone of OS , may hypervisor muna

• Hypervisor connects directly to OS

Type 1 Hypervisor

Installed first

• create necessary VMs and manages hardware resource

  • configure which core is assigned to which OS

Type 2 Hypervisor

• More convenient

• More latency because it deals with Host OS baggage

Type 1 vs Type 2

Type 1 Hypervisor (Bare Metal)

✅ Runs directly on hardware (bare metal), without an underlying OS
✅ More efficient & secure, used in enterprise environments
✅ Example Hypervisors:

• VMware ESXi

• Microsoft Hyper-V (bare metal mode)

• Xen

• KVM (Kernel-based Virtual Machine)

💡 Analogy:
💻 Type 1 is like a car with a built-in engine → Directly controls the hardware.

🔹 Pros:
✔ Faster performance (no OS overhead)
✔ More secure (isolated from OS vulnerabilities)
✔ Efficient resource management

🔹 Cons:
❌ Harder to set up and manage
❌ Requires dedicated hardware

Type 2 Hypervisor (Hosted)

✅ Runs on top of an existing OS (like Windows, Linux, macOS)
✅ Easier to install & use, but less efficient
✅ Example Hypervisors:

• VMware Workstation

• Oracle VirtualBox

• Microsoft Hyper-V (in Windows)

• Parallels Desktop (for macOS)

💡 Analogy:
💻 Type 2 is like a car with an external trailer engine → Runs on top of an existing system.

🔹 Pros:
✔ Easier to install & use
✔ No need for dedicated hardware
✔ Great for development & testing

🔹 Cons:
❌ Slower performance (because it depends on the host OS)
❌ More vulnerable to OS crashes & security risks

• 🏢 For enterprise servers & cloud computing → Use Type 1 (bare metal) for better performance & security.

• 🛠 For development, testing, or casual use → Use Type 2 (hosted) for ease of use.