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by sahaj 3928 days ago
N00b question. With more cores, wouldn't it also mean there's more overhead to "managing" process execution? There are probably some specific applications where it makes sense to have more cores, but does the everyday mobile user benefit from having thousands of cores?
2 comments
elihu 3928 days ago
Depends on the application. Ahmdahl's law comes into play; if there's a non-parallelizable component to what you're doing, it tends to dominate execution time. Managing lots of threads isn't really a big deal for modern operating systems, but communication between threads can be a big bottleneck.

Having lots of cores isn't likely to matter much for mobile users, simply because most mobile apps are neither optimized for parallelization nor CPU-hungry in the first place. If 4 cores are good enough, it doesn't matter if you add hundreds more. That said, there may be specific application that might benefit, such as computer vision.

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jeffreyrogers 3928 days ago
I think the consensus is that when you get to more than about 4 cores the performance benefits turn negative for general purpose computing.
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hyperpape 3927 days ago
I was surprised to hear this (though not because I know otherwise). What does general purpose computing mean in this context?
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jeffreyrogers 3927 days ago
Basically the workload that an average person is going to have: a bunch of processes running simultaneously with varying degrees of cpu and memory intensiveness.

In special cases you can get better performance with more, but less beefy cores (graphics is a prime example), but in general a few powerful cores performs better. The main reason is because communication among cores is hard and inefficient, so only embarrassingly parallel programs work well when divided among many cores. Plus the speedup you get from parallelize a program is minor in most cases. See Amdahl's law[1] for more on this topic.

Also, I'm not an expert in this area, but I have some familiarity with it. So hopefully someone with a bit more experience can come and confirm (or refute) what I've written.

[1]: https://en.wikipedia.org/wiki/Amdahl's_law

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