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Questions and Answers
What is one reason why a developer may need to understand the OS during development and debug?
What is one reason why a developer may need to understand the OS during development and debug?
What is a potential impact on an application's performance due to a system event?
What is a potential impact on an application's performance due to a system event?
Why may an application need to interface with a custom device?
Why may an application need to interface with a custom device?
What is one responsibility of an OS?
What is one responsibility of an OS?
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What is a potential reason for an application's slow performance?
What is a potential reason for an application's slow performance?
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What may be required to grant permissions and access to a user of an application?
What may be required to grant permissions and access to a user of an application?
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What may affect an application's performance due to the scheduling policy?
What may affect an application's performance due to the scheduling policy?
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Why is it important to understand the OS offerings for messaging between applications?
Why is it important to understand the OS offerings for messaging between applications?
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What is the purpose of an Operating System in managing process states?
What is the purpose of an Operating System in managing process states?
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Which of the following is NOT a state of a process in its lifecycle?
Which of the following is NOT a state of a process in its lifecycle?
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What does the 'Priority' field in a Process Control Block (PCB) refer to?
What does the 'Priority' field in a Process Control Block (PCB) refer to?
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What is the main reason why an OS tries to limit frequent transitions between CPU cores?
What is the main reason why an OS tries to limit frequent transitions between CPU cores?
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What information does the 'I/O status information' field in a PCB store?
What information does the 'I/O status information' field in a PCB store?
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What is the purpose of the 'Process ID' field in a PCB?
What is the purpose of the 'Process ID' field in a PCB?
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What is the purpose of the direct memory access controller in DMA?
What is the purpose of the direct memory access controller in DMA?
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What does the 'Pointer' field in a PCB refer to?
What does the 'Pointer' field in a PCB refer to?
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What is an intermediate layer that acts as a buffer to report data faster?
What is an intermediate layer that acts as a buffer to report data faster?
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What is the 'Ready' state of a process in its lifecycle?
What is the 'Ready' state of a process in its lifecycle?
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What is the mechanism where the OS grants authority to another controller to interrupt the CPU?
What is the mechanism where the OS grants authority to another controller to interrupt the CPU?
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What contains the addresses for all Interrupt Service Routines (ISR) in Interrupt-Driven I/O?
What contains the addresses for all Interrupt Service Routines (ISR) in Interrupt-Driven I/O?
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What is the purpose of polling or programmed I/O?
What is the purpose of polling or programmed I/O?
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What is unique for each device in Interrupt-Driven I/O?
What is unique for each device in Interrupt-Driven I/O?
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What is the main difference between polling and Interrupt-Driven I/O?
What is the main difference between polling and Interrupt-Driven I/O?
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What type of I/O is commonly used by most OSs?
What type of I/O is commonly used by most OSs?
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What is the primary reason why an OS needs to ensure that a file is not moved or deleted when it is in use?
What is the primary reason why an OS needs to ensure that a file is not moved or deleted when it is in use?
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What is the purpose of a garbage collector in an OS?
What is the purpose of a garbage collector in an OS?
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Why is access control necessary even in a single-user system?
Why is access control necessary even in a single-user system?
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What is the primary goal of concurrency control in an OS?
What is the primary goal of concurrency control in an OS?
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What happens when a user tries to delete a file that is currently in use?
What happens when a user tries to delete a file that is currently in use?
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What is the benefit of accessing a file with the required access level and mode?
What is the benefit of accessing a file with the required access level and mode?
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What is the purpose of marking unused files over a period of time?
What is the purpose of marking unused files over a period of time?
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Why is it necessary to protect critical devices on a system?
Why is it necessary to protect critical devices on a system?
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What happens when a process requests an I/O operation in synchronous I/O?
What happens when a process requests an I/O operation in synchronous I/O?
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What is the main purpose of synchronization in multi-threaded applications?
What is the main purpose of synchronization in multi-threaded applications?
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What is a mutex used for in synchronization?
What is a mutex used for in synchronization?
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What is the main difference between a mutex and a semaphore?
What is the main difference between a mutex and a semaphore?
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What happens when a process requests an I/O operation in asynchronous I/O?
What happens when a process requests an I/O operation in asynchronous I/O?
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What is the primary cause of race conditions in multi-threaded applications?
What is the primary cause of race conditions in multi-threaded applications?
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What is the purpose of a binary semaphore?
What is the purpose of a binary semaphore?
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What is the result of a race condition in multi-threaded applications?
What is the result of a race condition in multi-threaded applications?
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Study Notes
Inter-Process Communication (IPC) and OS
- The choice of IPC protocols depends on the OS offerings.
- During development and debug, understanding the OS is necessary to interact with it.
- Debugging a slowly performing or nonresponsive application requires understanding of OS's input/output operations.
Importance of Knowing the OS
- Understanding the OS helps in debugging applications.
- Questions to consider during debug:
- Are you accessing the file system too often and writing repeatedly to the disk?
- Is there a garbage collector in place by the software framework/SDK?
- Is the application holding physical memory information for too long?
- Is the application frequently creating and swapping pages in memory?
- What is the average commit size and page swap rate?
- Is there any other system event that could have affected performance?
- Is there an impact on the application based on the scheduling policy, application priority, and utilization levels?
Responsibilities of an OS
- The OS needs to abstract the complexities of the underlying hardware.
- The OS supports multiple users and facilitates execution of multiple applications at the same time.
- The OS manages process states: New, Running, Waiting, Ready, and Terminated or Exit.
- The OS schedules processes on multiple CPU cores, trying to limit context switching between cores.
Process Control Block (PCB)
- The PCB contains:
- Process ID (unique identifier)
- Process state (current state of the process)
- Pointer (hierarchy of processes)
- Priority (level of priority)
- Program counter (current instruction)
- CPU registers (register details)
- Memory management info (memory details)
- I/O status information (I/O details)
- Accounting information (usage details)
Memory Management
- Memory-Mapped I/O: allows devices to access memory directly
- Direct Memory Access (DMA): allows devices to transfer data without involving the CPU
Interrupt Handling Mechanisms
- Polling or programmed I/O: the OS checks for interrupt information periodically
- Interrupt-Driven I/O: the OS uses an interrupt vector to handle interrupts
Synchronous vs. Asynchronous I/O
- Synchronous I/O: the process waits for I/O operation to complete
- Asynchronous I/O: the process continues while I/O operation is in progress
Synchronization and Critical Sections
- In multi-threaded applications, access to shared variables needs to be synchronized to avoid race conditions.
- The OS provides mutexes and semaphores to coordinate access to shared resources.
Mutex and Semaphore
- Mutex: used for mutual exclusion, allowing only one process to access a resource at a time
- Semaphore: a generalized mutex, used to coordinate access to shared resources
Concurrency and Cleanup Control
- The OS ensures that files are not moved or deleted when in use.
- The OS needs to periodically clean up temporarily created files that are no longer required.
- The OS uses a garbage collector to mark unused files for deletion.
Access and Protection
- User Mode and Kernel Mode (Rings): the OS has different levels of access and protection.
- The OS needs to protect program resources from other applications and critical devices on the system.
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Description
Learn about the factors influencing the choice of inter-process communication protocols in different operating systems and how to debug performance issues.