Apple Open Sources Snow Leopard's Grand Central Dispatch (Apple Insider) [LWN.net]

Apple Open Sources Snow Leopard's Grand Central Dispatch (Apple Insider)

Posted Sep 14, 2009 16:48 UTC (Mon) by malor (guest, #2973)
In reply to: Apple Open Sources Snow Leopard's Grand Central Dispatch (Apple Insider) by epa
Parent article: Apple Open Sources Snow Leopard's Grand Central Dispatch (Apple Insider)

just start 500 threads

That seems better than guessing how many threads to start at once.

You're still more or less guessing with that 500.

And yeah, the kernel probably would be a better place, but this kind of rich management API seems very against the minimalist Linux kernel team ethos. It strikes me that they'd insist, whether rightly or wrongly, that an API with this much management (like dependencies and subqueues) would have to be implemented in user space, which goes right back to GCD.

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Apple Open Sources Snow Leopard's Grand Central Dispatch (Apple Insider)

Posted Sep 16, 2009 11:58 UTC (Wed) by epa (subscriber, #39769) [Link]

I'm not suggesting any kind of rich management API - just a scheduling class that runs threads one at a time and never pre-empts one thread to run another. If they are all batch jobs and all of the same priority, there is no need for preemption.

You're right, the choice to start 500 threads is itself a bit arbitrary. What I mean is if you know that (for whatever reason) you want to start 500, why hold back for fear of overwhelming the poor kernel with too many at once? Surely you should just be able to create them, and the kernel will decide for itself when to schedule each one.