The Multi-Core Dilemma Goes Mainstream
John Markoff of The New York Times published an interesting article on today entitled “Faster Chips Are Leaving Programmers in Their Dust“.
It’s great to see that this challenge, which I’ve been calling the Multi-core Dilemma is now moving into the mainstream discussion. Of course, I was far from the first to sound the alarm here, but it’s good to see the broader discussion now taking place. We need to be talking about these issues and delivering practical solutions. For everyone who writes software, this is a significant challenge but also a significant opportunity. The approach to addressing this is “concurrent computing” or simply, “Concurrency”.
Concurrency is a discipline that will become increasingly important in software development. In fact, expect it to be a skill that employers look for on technical resumes in the not-too-distant future. Of course, Concurrency is not new, it’s almost as old as computing itself. But as Herb Sutter pointed out in this article in Dr. Dobbs; “The Free Lunch Is Over“, it was only required for a relatively small percentage of applications until recently. With multi-core and many-core hardware now a reality, Concurrency is already required for a significant percentage of applications and will soon be the norm.
As cited in the Times article, several companies, including Microsoft, are working on new programming languages that are designed from the ground-up for Concurrency. That is undoubtedly the right direction, but these efforts are years from being mainstream technology. When they are ready, they are likely to be applicable mostly to new development - new code will be concurrent from the start. But where does this leave the billions (yes, billions with a “B”) of lines of code that businesses already have running in their data centers?
There are a variety of threading packages available, including Rogue Wave’s SourcePro Threads for building concurrent applications. These tools make the process easier by handling much of the threading work so that software developers don’t have to. But even with these it is complex and there is still a lot of design and testing work to be done. Testing multi-threaded applications is tricky. Even with thorough testing, problems often don’t arise until the application is in production.There are many factors to consider in the Concurrency discussion, but here is one aspect to consider. With the widening adoption of Service Oriented Architectures (SOA), we need to address Concurrency at the inter-service level as well as intra-service. Threading libraries and packages are well established approaches for intra-service, but there aren’t a lot of good solutions for inter-service Concurrency other than things like clusters - but that is a blunt instrument for this task.
Concurrency at the service level (inter-service) can have several benefits.First, this approach has the affect of abstracting the Concurrency model away from the application logic. This “loose coupling of concurrency” makes it easier to change your concurrency model - such as when you move from a 4-core to a 16-core server - without touching your application code. Second, it is easier to apply to existing applications since it treats the individual service largely as a black box. Third, it can provide the scale-out that traditionally came from clustering but with much more intelligence, since the application logic is part of the mix.
In summary, there are several important needs here that have not been adequately addressed:
1. Solutions that apply Concurrency to existing applications without significant rewriting
2. Inter-service Concurrency to abstract the Concurrency model from the application code
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