Performance analysis laughable

Article: Medfield, Intel's x86 Phone Chip
By: observer (no.thanks.delete@this.for.now), January 26, 2012 4:17 am
Room: Moderated Discussions
Wilco (Wilco.Dijkstra@ntlworld.com) on 1/25/12 wrote:
---------------------------
>none (none@arm.com) on 1/25/12 wrote:
>---------------------------
>>Wilco (Wilco.Dijkstra@ntlworld.com) on 1/25/12 wrote:
>>---------------------------
>>[...]
>>>Running micro benchmarks like Dhrystone/CoreMark gives close to maximum power consumption.
>>
>>Hu? Neither of them makes use of floating-point or SIMD
>>(unless you have strcmp implemented as SIMD instructions in
>>your C lib). Neither of them have heavy miss traffic.
>>Neither of them completely kill branch predicition. So how
>>could they represent maximum power consumption on anything
>>but a cache-less, FP-less, bpred-less CPU?
>
>When a core is stalled on memory, it actually uses very little power due to extensive
>clock gating. With heavy branch misprediction you flush the pipeline all the time,
>which means you have only executed some of the fetched instructions. Very branchy
>but well predicted code would do the same number of fetches but execute far more
>instructions, thus using more power overall.
A predicted branch would be predicted either taken or not taken, so fetching would start working on either of those paths, right? High performance "deeply" pipelined instruction fetch costs power in my experience... not much difference in power for correct / incorrect predictions, but correct predictions reduce execution time -> lowering the energy consumption for a given task. Could you elaborate why this would be very different for the core you had in mind? Disregarding execution unit power that is.
>
>Old StrongARM figures at http://www.hpl.hp.com/hpjournal/dtj/vol9num1/vol9num1art5.pdf
>show decode+execute used 26% of total power, while caches used 60%. So getting
>as many L1 I&D hits as possible was the way to get maximum power. Dhrystone fits
>that scenario pretty well (note the paper explicitly mentions it is the maximum
>power consumption case), and I know it was used extensively at ARM for power consumption
>estimates. You've got a point about VFP/Neon not being used - that would certainly
>matter if you can issue more instructions after maxing out the L1.
>
>Wilco
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Medfield article onlineDavid Kanter2012/01/23 01:51 PM
  server errorbakaneko2012/01/24 03:00 AM
    FixedDavid Kanter2012/01/24 04:02 AM
      FixedJoel2012/01/24 07:43 AM
      FixedRicardo B2012/01/24 11:25 AM
        FixedDavid Kanter2012/01/24 05:29 PM
      FixedGabriele Svelto2012/01/24 01:07 PM
        FixedDavid Kanter2012/01/24 05:30 PM
  Reference platform battery lifeDoug Siebert2012/01/24 02:03 PM
    standby timeFoo_2012/01/25 06:58 AM
      standby timeAnon2012/01/26 03:42 AM
        standby timeFoo_2012/01/26 04:02 AM
          standby timeDoug Siebert2012/01/26 12:39 PM
            standby timeAnon2012/01/26 01:22 PM
              standby timeanon2012/01/26 02:08 PM
                standby timeAnon2012/01/26 06:03 PM
                  standby timeanon2012/01/26 08:57 PM
                    standby timeanon2012/01/26 09:01 PM
                    standby timeAnon2012/01/27 09:32 PM
                standby timeDoug Siebert2012/01/27 02:15 PM
                  standby timeanon2012/01/27 02:41 PM
    Reference platform battery lifeDavid Kanter2012/01/27 10:09 AM
  Performance analysis laughableWilco2012/01/24 03:23 PM
    Performance analysis laughableDavid Kanter2012/01/24 05:19 PM
      Performance analysis laughableIntelUser20002012/01/24 07:30 PM
        Performance analysis laughableIntelUser20002012/01/24 07:32 PM
        Performance analysis laughableDavid Kanter2012/01/24 11:34 PM
          Performance analysis laughableIntelUser20002012/01/24 11:56 PM
            Performance analysis laughableDavid Kanter2012/01/25 02:07 AM
              Performance analysis laughableAlberto2012/01/25 12:54 PM
          Atom HT gainWilco2012/01/25 05:43 AM
            Atom HT gainIntelUser20002012/01/25 06:53 AM
              Atom HT gainnone2012/01/25 07:04 AM
                Atom HT gainIntelUser20002012/01/25 07:35 AM
            Atom HT gainFoo_2012/01/25 07:06 AM
      Performance analysis laughableWilco2012/01/24 08:21 PM
        Performance analysis laughableDavid Kanter2012/01/24 10:13 PM
          Performance analysis laughableWilco2012/01/25 04:30 AM
            Performance analysis laughablenone2012/01/25 06:14 AM
              Performance analysis laughableWilco2012/01/25 07:18 AM
                Performance analysis laughableobserver2012/01/26 04:17 AM
                  Performance analysis laughableWilco2012/01/26 06:25 AM
            Process numbersAlberto2012/01/26 09:29 AM
            Performance analysis laughableDavid Kanter2012/02/02 12:38 AM
          Performance analysis laughabletupper2012/01/25 04:27 PM
            Performance analysis laughableLinus Torvalds2012/01/25 08:37 PM
              Performance analysis laughableDoug Siebert2012/01/26 02:12 PM
  Medfield article onlineAndreas2012/01/25 03:10 AM
    Medfield article onlineAlberto2012/01/25 09:44 AM
    Medfield article onlineIntelUser20002012/01/25 10:24 AM
    Medfield article onlineDavid Kanter2012/01/25 09:58 PM
      Medfield article onlineDoug Siebert2012/01/26 01:20 PM
        Medfield article onlineEric2012/01/26 06:10 PM
          Medfield article onlineDoug Siebert2012/01/27 02:40 PM
  64-bitIngeneer2012/01/25 09:28 AM
    64-bitFoo_2012/01/25 10:23 AM
      64-bitIngeneer2012/01/25 02:34 PM
        64-bitUngo2012/01/25 04:08 PM
          64-bitEduardoS2012/01/26 12:55 PM
  Saltwell memcpySHK2012/01/26 02:41 AM
  Medfield WiFi & BluetoothRob Thorpe2012/01/26 03:09 AM
    Medfield WiFi & BluetoothDavid Kanter2012/01/27 05:54 PM
      Medfield WiFi & BluetoothRob Thorpe2012/01/28 02:22 PM
  Medfield article online (NT)Anil2012/01/26 05:57 PM
  Medfield article onlineAnil2012/01/26 06:11 PM
    Medfield article onlineMr. Camel2012/01/26 06:26 PM
    Medfield article onlinenone2012/01/27 01:41 AM
Reply to this Topic
Name:
Email:
Topic:
Body: No Text
How do you spell avocado?