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Measuring Real-World Power Consumption, Part Two

First, we wanted to check if the Interlagos power management problems were specific to ESXi. Therefore, we measured the power consumption when running Windows 2008 R2 SP1 x64. We set the power management policy to "Balanced" and "High Performance".

Windows Server 2008 R2 Idle Power consumption

Wow, that is a lot better! The core gating of the Bulldozer cores is first rate, as good as the Xeons of today. Idle power draw is a serious problem of the Opteron 6174: it is between 30 to 63% higher! So even if the ESX scheduler does not really understand how to handle the power management features of the "Bulldozer" Opteron, the question remains why the Opteron 6276 cannot even beat the Opteron 6174 when running idle in ESXi.

ESX 5.0

While I was testing the power consumption on Windows, my colleague Tijl Deneut dug up some interesting information about the ESX power manager. The Balanced Power policy (the default power policy for ESXi 5) is rather simple: it uses an algorithm that exploits only the processor’s P-states and C-state C0 and C1. So "Balanced" does not make very good use of the deeper sleep states. So we went for custom, which is the same as "Balanced" until you start to customize of course. We enabled the other C-states and things started to make sense.

ESX 5.0

After some tinkering, the Opteron 6276 does quite a bit better and saves 17W (10%). The Xeon reduces power consumption by 3W, and the Opteron 6174's less advanced power management is not able to save any more power. So enabling the C-states is an important way to improve the power consumption of the Opteron "Interlagos" with ESXi 5.

Virtualization Performance: ESX + Windows Power Management in Windows Server 2008 SP2
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  • JohanAnandtech - Thursday, November 17, 2011 - link


    1) Niagara is NOT a CMT. It is interleaved multipthreading with SMT on top.

    I haven't studied the latest Niagaras but the T1 was a fine grained mult-threaded CPU. It switched like a gatling gun between threads, and could not execute two threads at the same time.
    Reply
  • Penti - Thursday, November 17, 2011 - link

    SPARC T2 and onwards has additional ALU/AGU resources for a half physical two thread (four logically) solution per core with shared scheduler/pipeline if I remember correctly. That's not when CMT entered the picture according to SUN and Sun engineers any way. They regard the T1 as CMT as it's chip level. It's not just a CMP-chip any how. SMT is just running multiple threads on the cpus, CMP is working the same as SMP on separate sockets. It is not the same as AMDs solution however. Reply
  • Phylyp - Tuesday, November 15, 2011 - link

    Firstly, this was a very good article, with a lot of information, especially the bits about the differences between server and desktop workloads.

    Secondly, it does seem that you need to tune either the software (power management settings) or the chip (CMT) to get the best results from the processor. So, what advise is AMD offering its customers in terms of this tuning? I wouldn't want to pony up hundreds of dollars to have to then search the web for little titbits like switching off CMT in certain cases, or enabling High-performance power management.

    Thirdly, why is the BIOS reporting 32 MB of L2 cache instead of 8 MB?
    Reply
  • mino - Wednesday, November 16, 2011 - link

    No need for tuning - turbo is OS-independent (unless OS power management explicitly disables it aka Windows).
    Just disable the power management on the OS level (= high performance fro Windows) and you are good to go.
    Reply
  • JohanAnandtech - Thursday, November 17, 2011 - link

    The BIOS is simply wrong. It should have read 16 MB (2 orochi dies of 8 MB L3) Reply
  • gamoniac - Tuesday, November 15, 2011 - link

    Thanks, Johan. I run HyperV on Windows Server 2008 R2 SP1 on Phonem II X6 (my workstation) and have noticed the same CPU issue. I previously fixed it by disabling AMD's Cool'n'Quiet BIOS setting. After switching to high performance increase my overall power usage by 9 watts but corrected the CPU capping issue you mentioned.

    Yet another excellent article from AnandTech. Well done. This is how I don't mind spending 1 hour of my precious evening time.
    Reply
  • mczak - Tuesday, November 15, 2011 - link

    L1 data and instruction cache are swapped (instruction is 8x64kB 2-way data is 16x16kB 4-way)
    L2 is 8x2MB 16-way
    Reply
  • JohanAnandtech - Thursday, November 17, 2011 - link

    fixed. My apologies. Reply
  • hechacker1 - Tuesday, November 15, 2011 - link

    Curious if those syscalls for virtualization were improved at all. I remember Intel touting they improved the latency each generation.

    http://www.anandtech.com/show/2480/9

    I'm guessing it's worse considering the increased general cache latency? I'm not sure how the latency, or syscall, is related if at all.

    Just curious as when I do lots of compiling in a guest VM (Gentoo doing lots of checking of packages and hardware capabilities each compile) it tends to spend the majority of time in the kernel context.
    Reply
  • hechacker1 - Tuesday, November 15, 2011 - link

    Just also wanted to add: Before I had a VT-x enabled chip, it was unbearably slow to compile software in a guest VM. I remember measuring latencies of seconds for some operations.

    After getting an i7 920 with VT-x, it considerably improved, and most operations are in the hundred or so millisecond range (measured with latencytop).

    I'm not sure how the latests chips fare.
    Reply

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