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hwloc 1.0 released!

At long last, we have released a stable, production-quality version of Hardware Locality (hwloc).  Yay!

If you’ve missed all my prior discussions about hwloc, hwloc provides command line tools and a C API to obtain the hierarchical map of key computing elements, such as: NUMA memory nodes, shared caches, processor sockets, processor cores, and processing units (logical processors or “threads”). hwloc also gathers various attributes such as cache and memory information, and is portable across a variety of different operating systems and platforms.

In an increasing NUMA (and NUNA!) world, hwloc is a valuable tool for high performance.

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Do you use the MPI C++ bindings?

Do you use the MPI C++ bindings in real-world MPI applications?

I’m not talking about using the MPI C bindings in C++ MPI applications (e.g., using MPI_Send() — a C binding).  I’m talking about writing substantial C++ MPI applications that use the MPI C++ bindings (such as MPI::Send()). 

Do you do that?  Post a comment below and let me know.

The reason that I ask is because there is some confusion in the MPI Forum as to exactly how many people use the MPI C++ bindings — and whether we should un-deprecate the MPI C++ bindings. 

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ummunotify hits the -mm kernel tree

The “ummunotify” functionality was been added to the “-mm” Linux kernel tree yesterday.

/me does a happy dance

Granted, getting into the -mm tree doesn’t guarantee anything about getting into Linus’ tree.  But it’s definitely steps in the right direction.

Let me tell you why this is a Big Deal: memory management of networks based on OS-bypass techniques are a nightmare.  Ummunotify makes it slightly less of a nightmare.  This is good for MPI implementations and good for real-world MPI applications.

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More traffic

Traffic.  I find myself still thinking about my last entry today as I’m riding the blue line CTA from O’Hare airport to downtown Chicago for the MPI Forum meeting this afternoon.  Here I am, being spirited downtown at a steady clip on a commuter train while I see thousands of gridlocked cars on one side of me, and easily flowing motor vehicles on the other.  I will definitely reach downtown before the majority of vehicles that are only a few feet away from me on the Kennedy expressway, despite the fact that I’m quite sure that I left O’Hare long after they did.

Traffic is such a great network metaphor that is gives insight into today’s ramble: it’s well-understood that network packets may be delivered in a different order than which they were sent.  What’s less understood is why.

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Traffic

Traffic.  It’s a funny thing.  On my daily drive to work, I see (what appear to be) oddities and contradictions frequently.  For example, although the lanes on my side of the highway are running fast and clear, the other side is all jammed up.  But a half mile later, the other side is running fast and clear, and my lanes have been reduced to half-speed.  A short distance further, I’m zipping along again at 55mph (ahem).

Sometimes the reasons behind traffic congestion are obvious.  For example, when you drive through a busy interchange, it’s easy to understand how lots of vehicles entering and exiting the roadway can force you to slow down.  But sometimes the traffic flow issues are quite subtle; congestion may be caused by a non-obvious confluence of second- and third-order effects.

The parallels from highway traffic to networking are quite obvious, but the analogy can go much deeper when you consider that modern computational clusters span multiple different networks — we’re entering an era of Non-Uniform Network Architectures (NUNAs).

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