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Multicore Requires OS Rework, Windows Expert Says
alphadogg writes "With chip makers continuing to increase the number of cores they include on each new generation of their processors, perhaps it's time to rethink the basic architecture of today's operating systems, suggested Dave Probert, a kernel architect within the Windows core operating systems division at Microsoft. The current approach to harnessing the power of multicore processors is complicated and not entirely successful, he argued. The key may not be in throwing more energy into refining techniques such as parallel programming, but rather rethinking the basic abstractions that make up the operating systems model. Today's computers don't get enough performance out of their multicore chips, Probert said. 'Why should you ever, with all this parallel hardware, ever be waiting for your computer?' he asked. Probert made his presentation at the University of Illinois at Urbana-Champaign's Universal Parallel Computing Research Center."
If we want efficient code, we have to figure out ways to reward the programmers that write it. I don't see any sign that people anywhere are interested in doing this. Anyone have suggestions for how it might be done?
It's happening, from a source people didn't expect: portable devices. Battery life is becoming a primary feature of portable devices, and a large fraction of that comes from software efficiency. Take your average cell phone: it's probably got a half dozen cores running in it. One in the wifi, one in the baseband, maybe one doing voice codec, another doing audio decode, one (or more) doing video decode and/or 3d, and some others hiding away doing odds and ends.
The portable devices industry has been doing multi-core for ages. It's how your average cell phone manages immense power savings: you can power on/off those cores as necessary, switch their frequencies, and so on. They have engineers who understand how to do this. They're rewarded for getting it right: the reward is it lives on battery longer, and it's measurable.
Yes, you can get lazy and say 'next generation CPUs will be more efficient', but you'll be beaten by your competitors for battery life. Or, you fit a bigger battery and you lose in form factor.
The world is going mobile, and that'll be the push we need to get software efficient again.
I've always thought that both data flow languages and fortran95 had some innovations for multi-core programming worthy of being copied.
Data flow languages such as "G" which is sold as national instruments "labview" brand are intrinsically parallel at many levels. What they do is look at a function call as a list of unsatisfied inputs. These inputs are waiting for the data to arrive to make the variables valid. Then the subroutine fires. Thus every single function is potenitally a parallel process. it's just waiting on it's data. If you program in a serial fashion then of course those functions get called serially. But with graphic programming in 2D, you almost never are programming serially. You are just wiring outputs of other functions to inputs of others. Serial dependencies do arise but these are asynchronous and localized cliques. everything else is parallel. Yet you never ever ever actually write parallel code. it just happens automatically. Perl data language had a glimpse of this but it's not the same thing since the language is still perl and thus not parallel.
Objective-C with it's "message passing" abstraction is perhaps getting closer to the idea of a data flow. While one might complain that well objective-C message passing is just a different sugar coating of C just like C++ is. This would be true from the user's point of view. But it's not as true from the Operating system's point of view. IN OSX, these messages are passing more like actual socket programming at the kernel level. So there's more to objective C on apple's than meets the eye. But I don't know how far you can push that abstraction.
In fortran there are some rather simple but powerful multi-processor optimizations. First there's loops like "forall" that designate that a loop can be done in any order of the loop index and even in parallel. and then there's vectorized statements as part of the language like matrix multiplies. those are rather simple things so don't solve much but they do show that you can put a lot of compiler hinting into the language itself without re-inventing the language.
Some drink at the fountain of knowledge. Others just gargle.