Battery vs Performance

By: Doug S (, September 13, 2021 2:05 pm
Room: Moderated Discussions
Mark Roulo ( on September 13, 2021 1:18 pm wrote:
> David Hess ( on September 13, 2021 1:00 pm wrote:
> > Daniel B ( on September 13, 2021 5:20 am wrote:
> > >
> > > Either the scheduler needs to learn the application behaviour
> > > or the application should come tagged, but then the ISV
> > > is expected to understand hardware and system energy
> > > efficiency, which they don't.
> >
> > Is there any reason not to expect applications to lie? Of course every
> > thread needs to operate on the fastest available core. Ask them.
> >
> > Alternatively why would developers spend time to distinguish which threads should operate on which cores
> > when the result can only make the perceived performance worse? And why risk getting it wrong?

> >
> For mobile devices, at least, apps that use up the battery quickly risk being deleted. So for mobile
> devices there is risk in both directions: (a) running too slowly, or (b) eating the battery.
> I don't know how MUCH the battery life thing matters (I deleted a game that used too much
> battery, but ... sample size of 1) and maybe for laptops it really isn't important?

That assumes you can identify these apps. Apple (and I assume Android) has a screen where you can display the percentage of battery used by each app but unless you cross reference with a second screen that displays the percentage of "screen time" you can't tell whether it is above or below the average. Unless you are fairly technically proficient, you don't know whether some app has a reason to use battery above that average (i.e. a game with demanding graphics) or should use battery below average (i.e. a "book reader" app) Those two cases may be obvious, but most aren't. Even people here who are obviously much more technically capable than the average smartphone owner would have trouble determining whether a given app has a reason to use more or less power than the average.

So I'm skeptical that the average iPhone or Android owner could figure out which apps are using "too much" battery - especially if that extra usage is merely due to insistence on scheduling itself on the big cores at highest clock rates. A poorly written app might require 5x the instruction count per unit of "function" versus a well written app. If that well written app insists on scheduling on big cores maybe it uses 2x the power it would otherwise. It would still use only 40% the power of the poorly written app - so you still can't tell which apps are wasting battery unnecessarily by self-scheduling.

Allowing apps to determine where their threads should run would be like turning back the clock to the cooperative multitasking days. You have to rely on all apps being "good citizens" which is simply not realistic. Even if you 'reviewing' apps manually like Apple you can't possible test all the corner cases, and do a full re-test for every update.
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TopicPosted ByDate
alder lake.inteluser2021/09/10 01:52 AM
  alder lake.Andrei F2021/09/10 09:31 AM
    alder lake.Andrey2021/09/10 09:38 AM
      alder lake.rwessel2021/09/10 11:18 AM
      alder lake.Andrei F2021/09/10 12:49 PM
        alder lake.Andrey2021/09/10 04:12 PM
          alder lake.David Hess2021/09/10 07:39 PM
            alder lake.Andrey2021/09/11 12:28 AM
        alder lake.---2021/09/10 05:24 PM
          alder lake.Andrei F2021/09/12 01:09 AM
            DVFSDavid Kanter2021/09/12 09:58 PM
              DVFSAndrei F2021/09/13 01:02 AM
                DVFSAnon2021/09/13 03:28 AM
                DVFSJukka Larja2021/09/13 05:35 AM
                  DVFSAndrei F2021/09/14 12:07 AM
                    DVFSJukka Larja2021/09/14 04:11 AM
                      DVFSAndrei F2021/09/14 07:55 AM
                        DVFSJukka Larja2021/09/14 10:23 AM
                DVFS---2021/09/13 10:19 AM
                  DVFSDoug S2021/09/13 10:57 AM
                    DVFSDavid Hess2021/09/13 11:32 AM
                    DVFS---2021/09/13 01:06 PM
                      DVFSDavid Hess2021/09/13 02:21 PM
                    DVFSDavid Kanter2021/09/15 03:05 PM
                  DVFSDavid Hess2021/09/13 11:46 AM
                  DVFSJukka Larja2021/09/14 04:35 AM
                Quick shutdown?David Kanter2021/09/15 10:46 AM
                  Quick shutdown?Andrei F2021/09/16 07:12 AM
                    Quick shutdown?David Kanter2021/09/16 11:04 AM
                      Quick shutdown?Andrei F2021/09/17 01:35 AM
                        Quick shutdown?Andrei F2021/09/17 01:38 AM
            and weren't 'they' right?Daniel B2021/09/13 04:20 AM
              and weren't 'they' right?Andrei F2021/09/13 04:51 AM
                and weren't 'they' right?Daniel B2021/09/13 06:29 AM
              and weren't 'they' right?anon2021/09/13 05:07 AM
                and weren't 'they' right?Jukka Larja2021/09/13 05:26 AM
                  and weren't 'they' right?anon2021/09/13 11:37 PM
              Alder Lake has no little coresHeikki Kultala2021/09/13 06:33 AM
                Alder Lake has no little coresMichael S2021/09/13 07:33 AM
                  Alder Lake has no little coresme2021/09/13 10:45 AM
                  Alder Lake has no little coresHeikki Kultala2021/09/13 01:49 PM
                    Alder Lake has no little coresanon2021/09/13 11:42 PM
                why stop at two core sizes?hobold2021/09/14 05:47 AM
                  Memory caches did this, right?Mark Roulo2021/09/14 02:51 PM
                    Memory caches did this, right?Brett2021/09/14 07:17 PM
                      Memory caches did this, right?Kevin G2021/09/16 03:10 PM
                  Large reorder buffers (L1+L2)2021/09/15 11:24 AM
                    Large reorder buffers (L1+L2)hobold2021/09/15 12:06 PM
                Alder Lake has no little coresAdrian2021/09/14 08:33 AM
              and weren't 'they' right?David Hess2021/09/13 12:00 PM
                Battery vs PerformanceMark Roulo2021/09/13 12:18 PM
                  Battery vs PerformanceDoug S2021/09/13 02:05 PM
                    Battery vs PerformanceDavid Hess2021/09/13 02:28 PM
                      Battery vs Performance---2021/09/13 05:08 PM
                      Battery vs Performance---2021/09/13 05:08 PM
                      Battery vs PerformanceDoug S2021/09/13 08:53 PM
                    Battery vs PerformanceAnon2021/09/14 06:42 AM
                and weren't 'they' right?Daniel B2021/09/13 12:57 PM
                  and weren't 'they' right?David Hess2021/09/13 02:11 PM
                    and weren't 'they' right?---2021/09/13 02:38 PM
                  and weren't 'they' right?---2021/09/13 02:32 PM
                and weren't 'they' right?Brendan2021/09/14 03:30 AM
                  and weren't 'they' right?Jukka Larja2021/09/14 04:31 AM
              and weren't 'they' right?Etienne Lorrain2021/09/14 12:29 AM
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