Browsing through a manufacturer’s website can offer a startling view of the product line up.  Such was the case when I sprawled through Gigabyte’s range, only to find that they offer server line products, including dual processor motherboards.  These are typically sold in a B2B environment (to system builders and integrators) rather than to the public, but after a couple of emails they were happy to send over their GA-7PESH1 model and a couple of Xeon CPUs for testing.  Coming from a background where we used dual processor systems for some serious CPU Workstation throughput, it was interesting to see how the Sandy Bridge-E Xeons compared to consumer grade hardware for getting the job done. 

In my recent academic career as a computational chemist, we developed our own code to solve issues of diffusion and migration.  This started with implicit grid solvers – everyone in the research group (coming from chemistry backgrounds rather than computer science backgrounds), as part of their training, wrote their own grid and solver classes in C++ which would be the backbone of the results obtained in their doctorate degree.  Due to the idiosyncratic nature of coders and learning how to code, some of the students naturally wrote classes were easily multi-threaded at a high level, whereas some used a large amount of localized cache which made multithreading impractical.  Nevertheless, single threaded performance was a major part in being able to obtain the results of the simulations which could last from seconds to weeks.  As part of my role in the group, I introduced the chemists to OpenMP which sped up some of their simulations, but as a result caused the shift in writing this code towards the multithreaded.  I orchestrated the purchasing of dual processor (DP) Nehalem workstations from Dell (the preferred source of IT equipment for the academic institution (despite my openness to build in-house custom hardware) in order to speed up the newly multithreaded code (with ECC memory for safety), and then embarked on my own research which looked at off-the-shelf FEM solvers then explicit calculations to parallelize the code at a low level, which took me to GPUs, which resulted in nine first author research papers overall in those three years. 

In a lot of the simulations written during that period by the multiple researchers, one element was consistent – trying to use as much processor power as possible.  When one of us needed more horsepower for a larger number of simulations, we used each other’s machines to get the job done quicker.  Thus when it came to purchasing those DP machines, I explored the SR-2 route and the possibility of self-building the machines, but this was quickly shot down by the IT department who preferred pre-built machines with a warranty.  In the end we purchased three dual E5520 systems, to give each machine 8 cores / 16 threads of processing power, as well as some ECC memory (thankfully the nature of the simulations required no more than a few megabytes each), to fit into the budget.  When I left that position, these machines were still going strong, with one colleague using all three to correlate the theoretical predictions with experimental results.

Since leaving that position and working for AnandTech, I still partake in exploring other avenues where my research could go into, albeit in my spare time without funding.  Thankfully moving to a single OCed Sandy Bridge-E processor let me keep the high level CPU code comparable to during the research group, even if I don’t have the ECC memory.  The GPU code is also faster, moving from a GTX480 during research to 580/680s now.  One of the benchmarks in my motherboard reviews is derived from one of my research papers – regular readers of our motherboard reviews will recognize the 3DPM benchmark from those reviews and in the review today, just to see how far computation has gone.  Being a chemist rather than a computer scientist, the code for this benchmark could be comparable to similar non-CompSci trained individuals – from a complexity point of view it is very basic, slightly optimized to perform faster calculations (FMA) but not the best it could be in terms of full blown SSE/SSE2/AVX extensions et al.

With the vast number of possible uses for high performance systems, it would be impossible for me to cover them all.  Johan de Gelas, our server reviewer, lives and breathes this type of technology, and hence his benchmark suite deals more with virtualization, VMs and database accessing.  As my perspective is usually from performance and utility, the review of this motherboard will be based around my history and perspective.  As I mentioned previously, this product is primarily B2B (business to business) rather than B2C (business to consumer), however from a home build standpoint, it offers an alternative to the two main Sandy Bridge-E based Xeon home-build workstation products in the market – the ASUS Z9PE-D8 WS and the EVGA SR-X.  Hopefully we will get these other products in as comparison points for you.

Gigabyte GA-7PESH1 Visual Inspection, Board Features
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  • Hakon - Saturday, January 5, 2013 - link

    Thank you for the detailed answer. I very much appreciate your article and hope to see more stuff like this on Anandtech.

    What I meant regarding to NUMA is the following. When you have a dual socket Xeon you have two memory controllers. The first time you 'touch' a memory location it is assigned to the memory controller of the CPU that runs the current thread. This assignment is in general permanent and all further memory read/writes to that location will be served by that memory controller.

    If you first-touch (e.g. initialize the array to zero) using one thread, then the whole array is assigned to one of the two memory controllers. When you then run the multi-threaded code on that array one memory controller is idle while the other is oversubscribed since it has to serve both CPUs.

    In contrast, if you first-touch your array in an OpenMP loop and use the same access pattern as in the algorithm, you will benefit from both memory controllers later on. In this case your large array is correctly 'distributed' over both memory controllers.

    This kind of memory layout optimization becomes extremely important when you deal with quad socket Opterons. You then have eight memory controllers. A NUMA aware code is therefore up to eight times as fast since it utilizes all memory controllers.
  • toyotabedzrock - Saturday, January 5, 2013 - link

    You should go ask the people on the assembly boards for help with making your code faster.

    They are very friendly compared to a Linux kernel devs, I think they just enjoy the acknowledgement that they still exist and are useful.
  • snajpa - Saturday, January 5, 2013 - link

    Blame the scheduler. Neither Windows nor linux can effectively handle larger NUMA systems. It randomly moves the process across the physical hardware.
  • psyq321 - Sunday, January 6, 2013 - link

    Hmm, this is definitely not true at least for Windows Server 2008 R2 / Windows 7, and I am sure it holds true for some versions of Linux (I am not a Linux expert).

    Windows Server 2008 R2 / Windows 7 scheduler will try to match the memory allocations (even if they are not tagged for a specific NUMA node) with the NUMA node the process/thread resides on, and they will not move a thread to a foreign NUMA node unless if that has been explicitly requested by the application (by setting the thread affinity)

    Of course, without explicit NUMA node tagging when doing allocations, application code is the main culprit for not respecting the NUMA layout (e.g. creating bunch of threads, allocating memory from one of them - and then pinning the threads to different CPUs - you will have lots of LLC requests from remote DRAM because memory was a-priori allocated on one node).

    For this - some sane coding helps a lot, here:

    I describe how I extracted more than double performance by careful memory allocation (NUMA-aware) - please note that neither Windows nor Linux scheduler is able to cope with code which is not written to be NUMA aware and it is using large number of threads that are supposed to run on all CPUs.. Simply put, application writer will have to manage memory allocation and usage in the way so that there are as little remote DRAM requests as possible.
  • snajpa - Sunday, January 6, 2013 - link

    About Windows scheduler - I only worked with Windows XP, now I don't have any reason to work with Win anymore, so what you say probably is really true. As for the linux versions - well, long story short, CFS sucks and everyone knows it - this is particularly noticeable if you have fully virtualized VMs which appear as one single process at the host system - the process is randomly swapped between CPU cores and even CPU dies.... sad story. That's why people have to pin their CPUs to their tasks manually.
  • psyq321 - Sunday, January 6, 2013 - link

    Ah, XP - that explains it. True, XP did not care about NUMA at all.

    Windows Server 2008 / Vista introduced NUMA-aware memory allocations, and changed their CPU scheduler so it does not move the thread across NUMA nodes. They will also try to allocate the memory from the thread's own NUMA node when legacy VirtualAlloc etc. APIs are used.

    Windows Server 2008 R2 / Windows 7 introduced the concept of CPU groups - allowing more than 64 CPUs. This does require some adaptation of the application, as old threading APIs only work with 64-bit affinity bitmask which only allowed recognizing 64 CPUs. Now, there is a new set of APIs that work with GROUP_AFFINITY structure, allowing control of CPU groups, too. However, this needs explicit change of the legacy process/threading APIs to the new ones.

    Furthermore, none of the above can replace some manual intervention*- while Windows scheduler will, indeed, respect NUMA node boundaries and not try to mess around with moving threads across them - it still does not know what the underlying algorithm wants to do.

    * There is no need to set the thread affinity to one specific CPU anymore - this prevents running the thread on any other CPU completely. Instead, there is an API called SetThreadIdealProcessor(Ex) which signals Windows scheduler that thread >should< run on that particular CPU - but, under certain circumstances the scheduler can move the thread somewhere else - if the CPU is completely taken away by some other thread/process. Scheduler will try to move the thread as close as possible - to the next core in the socket, for example - or to the next core in the group (group is always contained within a NUMA node).

    You can, however, absolutely forbid Windows scheduler from passing the thread to another NUMA node under any circumstances by simply getting the said NUMA node affinity mask (GetNumaNodeProcessorMask(Ex)) and setting this affinity as a thread affinity. This + setting the "ideal" processor still gives Windows scheduler some headroom to move the thread to another core if it is found to be better in a given moment, but it will not even attempt to cross the NUMA boundary in any case whatsoever.
  • lmcd - Monday, January 7, 2013 - link

    While I haven't personally researched them, there are tons of other schedulers that have been written for Linux and I'm certain *at least* one of them is more fitting to this line of work. I've heard of alternatives like BFS and the Linux kernel is so widely used I'm sure there's a gem out there for this application.
  • toyotabedzrock - Saturday, January 5, 2013 - link

    Have you ever tried the Intel Math Kernel Library? It might speed up some of the equations. It also hands off work to the Intel MIC card if it thinks it will speed it up.
  • KAlmquist - Saturday, January 5, 2013 - link

    The GA-7PESH1 motherboard is $855, and the CPU's are $2020 each, which adds up to $4895. On tasks which don't parallelize well, you can get similar performance from the i7-3770K, which costs an order of magnitude less. (Prices: i7-3770K $320, ASRock Z77 Extreme6 motherboard $152, total from motherboard and CPU $472.) On tasks which parallelize well enough that they can be run on a GPU, the system with the GA-7PESH1 will beat the i7-3770K, but will be crushed by a midrange GPU. So the price/performance of this system is pretty bad unless you throw just the right workload at it.

    The motherboard price from super-laptop-parts dot com, and the other prices are from a major online retailer that I won't name in order to get around the spam filter.
  • Death666Angel - Saturday, January 5, 2013 - link

    So, your 3770K has ECC memory or VT-D, TXT etc.?

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