Calxeda's ARM server tested
by Johan De Gelas on March 12, 2013 7:14 PM EST- Posted in
- IT Computing
- Arm
- Xeon
- Boston
- Calxeda
- server
- Enterprise CPUs
Measuring Bandwidth
Stream measures "sustainable memory bandwidth" and is thus a good indication of how a CPU will handle data intensive applications. Dr. John McCalpin is the developer and maintainer of the STREAM benchmark.
We compiled with gcc 4.7 on all platforms and used the -O3 -fopen -static settings. It is important to remark that this version of gcc has been optimized by the Linaro group, a non-profit software engineering effort. Linaro's objective is to optimize the kernel and typical tools for the ARM-Cortex A-series CPUs.
On the Intel CPUs we force the threads to make use of Hyper-Threading with taskset. So for example, the four threads measurement is done on two physical cores with four threads. This gives an idea of how a quad-core ARM server node compares to a virtual machine that gets a few physical and few logical cores from the hypervisor. It also allows us to evaluate how two threads on top of an Atom core compare to two ARM cores. When you compare CPUs with similar power consumption, you typically get two ARM cores for each Hyper-Threaded Atom core.
The ARM based server is a pretty bad choice right now for memory intensive workloads. Even with four cores and DDR3-1333, the useable bandwidth is less than one sixth of what one Xeon core can sustain.
In a similar vein, the ECX-1000 is not capable of providing more bandwidth than an Atom system equipped with DDR2-667. However, both the Atom and ARM cores are pretty bad when it comes to bandwidth. Although the specs claim that the CPUs can drive one channel of DDR3-1066, the measured bandwidth comes nowhere near the theoretical 8.5GB/s that such a DIMM can deliver.
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tech4real - Thursday, March 14, 2013 - link
Calxeda quotes 6W for the whole SOC. We don't know how much is used for all these uncore stuff. It's possible A9 core only burns around 800mW. Still quite a gap to 1.25W.Wilco1 - Thursday, March 14, 2013 - link
Assuming the 800mW figure is accurate and the uncore power stays the same, then a node would go from 6W to 7.8W - ie. 30% more power for 100% more performance. Or they could voltage scale down to 1.5GHz and get 65% more performance for 5% more power. While a 28nm A15 uses more power in both scenarios, it is also much faster, so perf/Watt is significantly better.tech4real - Thursday, March 14, 2013 - link
1. I guess we have to wait to see if it's really 2X perf from a9 to a15 in real tests. I personally wouldn't bet on that just yet.2. mostly likely the uncore power will increase too. i don't think the larger memory bandwidth will come free.
Wilco1 - Thursday, March 14, 2013 - link
1. We already know A15 is 50-60% faster than A9 per clock (and often more, particularly floating point), so that gives ~2x gain from 1.4GHz to 1.8GHz.2. The uncore power will be scaling down with process while the higher bandwidth demand from A15 will increase DRAM power. Without detailed figures it's reasonable to assume these balance each other out.
tech4real - Thursday, March 14, 2013 - link
then let's wait to see anand benchmarks the future a15 system.also since the real microserver battle is between the future a15 system and 22nm atom system, I am eager to see how it plays out.
Th-z - Wednesday, March 13, 2013 - link
Very interesting article, thanks! This really piques another curiosity: how does latest IBM Power based server fair these days.Flunk - Wednesday, March 13, 2013 - link
It really doesn't sound like the price\performance is there. Also, lack of Windows support makes it useless for those of us who run ASP.NET websites (like the company I work for).It's still nice to see companies trying something different from the standard strategy. Maybe this is be better in a few generations and take the web server market by storm. If we see a Windows Server arm I could see considering it as an option.
skyroski - Wednesday, March 13, 2013 - link
I agree your testing suite's method is good and ok, so you were testing in consideration with hosting providers, fair enough.However on the topic of if you were serving a single site would a standard Xeon be better or ARM based ones? Which - is the case of consideration to FB/Twitter/Google/Baidu etc..., whom are as I have been led to believe by the media this past year, companies that ARM partners are trying to sell this piece of kit to. This test unfortunately cannot tell us.
A quick search on Google on performance impact of VMs yielded a thread in the VMware community forum by a vExpert/Moderator that mentioned expectation of 90% performance, and frankly, no matter how small you think the performance impact of a VM maybe, it is still using up CPU cycles to emulate hardware, that point will remain true no matter how efficient the hypervisor gets.
Secondly, coupled with the overhead of running 24 physical copies of the OS + Apache + DB on a box that would otherwise be running a single copy of the OS + Apache + DB is total overkill (on that topic)
It would be great if you can also test Xeon's req/sec if it ran a single instance so we can see it from a different perspective, as of now as I said, your test is skewered towards hosting providers whom might invest in Calxeda to provide VPS alternatives. But to them (and their client base), the benefit of a VPS is it's portability, which, 24 physical ARM nodes isn't going to provide, so I don't see them considering it as an alternative solution anyway.
skyroski - Wednesday, March 13, 2013 - link
I also want to ask if your Xeon test server's network adapter is capable of and was using Intel VT-c?JohanAnandtech - Thursday, March 14, 2013 - link
It was using VMDq/Netqueue (via VMXnet) but not SR-IOV/VT-c