Parallelism at PDC: Day 3 - Concurrency Runtime
Niklas Gustafsson gave a "Deep Dive" talk on Microsoft's Concurrency Runtime. The Concurrency Runtime is a key feature in Microsoft's Visual Studio 2010.
Niklas started his talk by warning people it was a deep dive C++ oriented talk, one without glitz or performance data - but rather education and coding. A number of non-C++ programmers left the room appreciative of the 'heads-up' at the outset of the class. Niklas got a well deserved round of applause for his clarity.
Niklas invited me to join him on stage an talk about why we've been vocal at Intel about supporting Concurrency Runtime. In August, we went as far as to announce our support of this at the same time we announced our Intel Parallel Studio project.
I explained that year ago we consolidated on use of our own OpenMP runtime after some time of experimenting with various forms of parallelism in our math library vs. our compiler's implementation of OpenMP. Then, along came Intel Threading Building Blocks (TBB). For various reasons, TBB implemented it's own scheduler and thread pool completely separately from OpenMP. Next, Microsoft added to the mix with their own OpenMP in their compiler complete with their own solution for a thread pool. Throw in another threading package and you could quickly have 4X the software threads as you have hardware threads. Consider a two processor Intel Core I7 system, each being an 8-core, 16-thread processor. 4X subscription would mean a program creating 128 software threads for 32 hardware threads. The resulting pressure on memory and stacks will be unacceptable. We can survive with 2X on 2 core processors... but somewhere on the way to 64 hardware threads we will have a problem when programmers use more than one programming model.
If nothing else, threaded libraries make this a problem we must solve. Along comes Microsoft Concurrency Runtime.
Niklas walked us through the infrastructure that enables multiple concurrent programming models by allowing definition of multiple work schedulers working together with a central resource management system.
Microsoft's Concurrency Runtime encourages innovation at library and tool levels while solving key issues which would have been a big headache.