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Apple's Grand Central Dispatch Ported To FreeBSD
bonch writes "Apple's Grand Central Dispatch, which was recently open sourced, has been ported to FreeBSD and is planned to be included by default in FreeBSD 8.1. Also known as libdispatch, the API allows the use of function-based callbacks but will also support blocks if built using FreeBSD's clang compiler package. There's already discussion of modifying BSD's system tools to use the new technology." The port was originally unveiled last month at the 2009 Developer Summit in Cambridge. Slides from that presentation are available via the Dev Summit wiki.
GCD is far more encompassing than just spawning threads. It's mainly a library for task-based parallelization (my wording, not theirs) and has some other goodies in it as well.
For starters, unless it's not apparent by now, just spawning a new thread to run every such job is too heavy. Scheduling a new GCD job (and all of them will get run on one of a bunch of thread pool threads) is on the range of tens of CPU instructions; on Mac OS X, where GCD originated, spawning a new thread steals away in the vicinity of one megabyte (I can't seem to find an exact number) just for various bookkeeping. That's a lot of setup; even if there's a lot of fat to cut there, the best solution is probably not to spawn a new thread every time.
The API is also very neatly designed. Tasks can be created and added to groups or queues and run synchronously or asynchronously. Semaphores, queues and event sources (which will trigger the addition of an event handler to a queue automatically) can all be paused and resumed to more easily control the flow. Neat, especially combined with the creation of queues that you set up to just funnel work onto another queue.
Add to that the existence of several global queues with varying priorities (corresponding to a set of worker threads at each priority) and the potential for smarts for a system that can see the entire picture with regards to load within the program and across the system. I don't know the extent to which such smarts exist already, but I think you'll agree that with more metadata available, such a scheduler would be better equipped than one fiddling with coarser-grained threads.
So yeah, this is nothing like "just" spawning threads. (I've never worked directly with pthread; it may very well reuse threads, but it didn't look like it from the man page you referred to.) None of it, as far as I can tell, is Apple inventing something new and breakthrough, but it's still a damn good API with a good consolidated set of computationally cheap features whose level of abstraction solves problems.
Maybe someday we can actually have a modern desktop as responsive as BeOS was...
BeOS was indeed very responsive, but it was also notoriously difficult to program for. Apple seems to have done a great job at creating a powerful framework, while keeping it easy enough to be actually used by the developers.
It may be 7 digits, but at least it's a semiprime
Been there, done that on Solaris and Linux 10 years ago in plain old C. No magic required, just
and away you go.
Piece of cake! Of course, you have no idea how many other processes are tossing threads at their workload and so have no idea if this is a great time to spawn another 8 to really load out the CPU or whether you should just spawn 2 and let some other processes have their time. That's what GCD buys you.
Dewey, what part of this looks like authorities should be involved?
Several things didn't need to be open sourced, such as WebObjects and GCD. Quit your crying. FOSS zealots love to whine about Apple only doing what's required, but they fail to realize that it's a symbiotic relationship. Apple can use existing code to fit their needs, and in return, the open source community gets all of the improvements made by professional coders. It's a win/win, but the mini-Stallmans will never see it that way.
When is the last time that Apple released an entirely new project? For example Sun released ZFS under the CDDL.
Why reinvent the wheel? They adopt it, improve it and release the improvements. At least they add. They deliver. When is the last time Stallman released an entirely new project? Or finished one? "Although nearly all components have been completed long ago and have been in production use for a decade or more, its official kernel, GNU Hurd, is incomplete and not all GNU components work with it." from the reliable-as-ever Wikipedia. Apple is not Stallman. They do not serve the same market. Apple is in hardware/software/platform, Stallman is in philosophy. Fair enough, einen Unterschied muß es geben.
All those moments will be lost in time, like tears in rain. Time to die.
Well, we have the subject of this article, Grand Central Dispatch. We also have Darwin & XNU, their version of the Mach kernel. There is also Bonjour, their version of zeroconf, and their streaming server (Quicktime Streaming Server). They also purchased the source to gimp-print (now called Gutenprint) so they no longer have any obligation to keep it open source, but they do, and they keep releasing the source. How much more do you need?
Check out DRM-free movies at http://www.bside.com