Slashdot Mirror
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.
Grand Central is not introducing multithreading - it's introducing comprehensive thread management. So, how many threads are you going to spin for that task? Too many, and you waste a lot of time on thread management and preemption. Too few, and you have processors sitting idle. Now how will you handle this with multiple CPU's? Multiple cores? Hyperthreading? Different cache amounts and layout? OpenCL and GPU processing? Do you know what the rest of the operating system is doing to plan appropriately?
In short, your program can at best make a stab at these issues, and possibly even do a reasonable job if you put a lot of time, effort, and profiling into it. Or you could just use GCD, and let the framework handle it all for you, regardless of whether you're on a Core Solo Mac Mini or a Mac Pro with mutliple OpenCL graphics cards.
It's good stuff. And Apple gave it to the community (much like WebKit enhancements, launchd, etc).
I don't know what kind of crack I was on, but I suspect it was decaf.
Ars Technica has a great overview of what GCD is, and why it's important.
I haven't done much multithreaded programming in C, although this looks like an absolute godsend to those who do. Maybe someday we can actually have a modern desktop as responsive as BeOS was...
The article also contains a bit of information about Apple's compiler strategy and refinements to the C language itself. Most of these have been open-sourced under a permissive license, which is pretty damn cool.
-- If you try to fail and succeed, which have you done? - Uli's moose
Yep, apple didn't give back all their code on WebKit, or all of Darwin, or all of launchd, or all their patches on zfs, or their code on MacPorts, or darwin streaming server, or CalDav, or iCal format, or their Calander server, or their code on their X server, or their code on ruby, or a bunch of code on smart card services...
Wait, yes they did.