Processes, Threads, IPC ↩

Process

• Provides resoures to exec a program.
• Has :
  • Virtual address space
  • Executable code
  • Open handles to system objects
  • Security Context
  • Unique Process identifier
  • Environment variables
  • Priority Class
  • Max,Min working set sizes
  • At least 1 thread of execution
• Started with Primary thread but can create additional threads.

Thread

• Entity within a process that can be scheduled for execution.
• All threads share virtual address space and system resources.
• It has its own exception handlers, scheduling priority, local storage, unique identifier, and set of structures for state storage.
• Specific to one process.
• Pointers are process-specific so threads can share pointers.

Process vs Thread

Thread states

• Running thread enters blocked/suspended state if it’s blocked on waiting for some system resource, or its time splice expires.
• Blocked/Suspended threads become ready to run when the resource they wait on becomes available or when their sleep interval has expired.

Thread Features

• Managed threads : Interface to schedule and access threads over OS threads.
• Priority : Higher priority threads are preferred while scheduling.
• Foreground and Background Threads : Background threads do not keep the managed execution environment running. Once all foreground threads have been stopped in a managed process, so are the background threads.
• Thread Pool : Provides an app with a pool of worker threads that are managed by the system. Promotes concentration on app tasks.

Multithreading