Posts Tagged 'numactl'

Xeon E5-2600 OS CPU To Core / SMT Thread Mapping On Linux. It Matters.

Ages ago I blogged about the Intel topology tool and mapping Xeon 5500 (Nehalem EP) processor threads to OS CPUs on Linux. I don’t recall if I ever blogged the same about Xeon 5600 (Westmere EP) but I’ll cover that processor and Xeon E5-2600 in this short post.  Fist, Xeon 5600.

The following two screen shots are socket 0 and socket 1 from a Xeon 5600 server. Socket 0 first:

Now, socket 1:

So, based on the information above, one would have to specify OS CPUs 0,1,2,3,4,5 if they wanted thread 0 from the first 3 cores on each CPU (c0_t0). I never liked that much. That’s why I’m glad Sandy Bridge presents itself in a more logical manner. As you can see from the following two screen shots, specifying affinity for thread 0 of cores on socket 0 is as simple as 0,1,2,3,4,5,6,7. First, socket 0:

And now, socket 1:

Lest this come off as simple tomfoolery, allow me to show the 2x difference in siphoning off a fifo when the data flows socket-local versus socket-remote:

Be aware that this level of disparity will not necessarily be realized when a server is booted SUMA (nor even when BIOS NUMA is enabled but the grub boot string includes numa=off). I’d test the difference and blog that here but that would just be tomfoolery 🙂


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All content is © Kevin Closson and "Kevin Closson's Blog: Platforms, Databases, and Storage", 2006-2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Kevin Closson and Kevin Closson's Blog: Platforms, Databases, and Storage with appropriate and specific direction to the original content.

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