For operating systems, multi-core chips require new scheduling algorithms to make better use of the multiple cores available.On a multi-core chip, however, the threads could be spread across the available cores, allowing true parallel processing, as shown in Figure 4.4.įigure 4.3 - Concurrent execution on a single-core system.įigure 4.4 - Parallel execution on a multicore system A multi-threaded application running on a traditional single-core chip would have to interleave the threads, as shown in Figure 4.3.A recent trend in computer architecture is to produce chips with multiple cores, or CPUs on a single chip.when the load average is above some certain threshold. ( Note that single threaded processes can still benefit from multi-processor architectures when there are multiple processes contending for the CPU, i.e. Utilization of multiprocessor architectures - A single threaded process can only run on one CPU, no matter how many may be available, whereas the execution of a multi-threaded application may be split amongst available processors. Economy - Creating and managing threads ( and context switches between them ) is much faster than performing the same tasks for processes. ![]() Resource sharing - By default threads share common code, data, and other resources, which allows multiple tasks to be performed simultaneously in a single address space.Responsiveness - One thread may provide rapid response while other threads are blocked or slowed down doing intensive calculations.There are four major categories of benefits to multi-threading:.)įigure 4.2 - Multithreaded server architecture 4.1.2 Benefits A daemon would listen at a port, fork off a child for every incoming request to be processed, and then go back to listening to the port. ( The latter is how this sort of thing was done before the concept of threads was developed. Another example is a web server - Multiple threads allow for multiple requests to be satisfied simultaneously, without having to service requests sequentially or to fork off separate processes for every incoming request.For example in a word processor, a background thread may check spelling and grammar while a foreground thread processes user input ( keystrokes ), while yet a third thread loads images from the hard drive, and a fourth does periodic automatic backups of the file being edited.This is particularly true when one of the tasks may block, and it is desired to allow the other tasks to proceed without blocking.Threads are very useful in modern programming whenever a process has multiple tasks to perform independently of the others.As shown in Figure 4.1, multi-threaded applications have multiple threads within a single process, each having their own program counter, stack and set of registers, but sharing common code, data, and certain structures such as open files.įigure 4.1 - Single-threaded and multithreaded processes 4.1.1 Motivation.Traditional ( heavyweight ) processes have a single thread of control - There is one program counter, and one sequence of instructions that can be carried out at any given time.A thread is a basic unit of CPU utilization, consisting of a program counter, a stack, and a set of registers, ( and a thread ID.Abraham Silberschatz, Greg Gagne, and Peter Baer Galvin, "Operating System Concepts, Ninth Edition ", Chapter 4. So if you need to switch to another app to look something up, CourseNotes will pick up right where you left when you come back.ĬourseNotes 2.1 is available now in the iPad App Store for $4.99. ![]() What does multitasking mean for a note-taking app–can it keep taking notes while you do something else?  Not quite, but it does mean that when you switch to another app, CourseNotes will remember which subject or note session you were looking at when you come back.  And with the help of other tools that can sync with your iPad’s calendar, you can publish events to an online calendar right from CourseNotes!  Assignments and other ToDos will show up in your calendar with your title and note content, set to the due date you specify in the note. Now when you add a ToDo note, you can choose to sync it as an event to your iPad’s calendar. It’s finally possible to print over the air from the iPad, and CourseNotes is among the first apps to support this feature!  Choose a printer on your local network and print your CourseNotes notes right over the air! ![]() We’re happy to announce the release of CourseNotes 2.1 for the iPad, a release which takes full advantage of a number of new features available in iOS 4.2!  We’ve been eagerly awaiting the release of iOS 4.2 and the new functionality it would bring to the iPad ever since it was announced. CourseNotes 2.1: Printing, Calendar syncing & multitasking on iOS 4.2 Posted: November 22nd, 2010 | Author: jon | Filed under: CourseNotes App, iPad | Comments Off on CourseNotes 2.1: Printing, Calendar syncing & multitasking on iOS 4.2
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