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Bug Power Linux

Linux Kernel Suffering Power Management Regression? 186

Posted by Soulskill
from the year-of-linux-on-the-coppertop dept.
An anonymous reader writes "It appears that there's a big power management regression in the Linux kernel for the 2.6.38 and 2.6.39 development releases, including the kernel to ship with Ubuntu 11.04 next week. It's reportedly causing a 10~30% increase in power consumption on many laptop computers."
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Linux Kernel Suffering Power Management Regression?

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  • by Anonymous Coward on Friday April 22, 2011 @06:20PM (#35910714)
    I think this is something that only Power Users will notice. It's not something important for the common user.
    • I think this is something that only Power Users will notice. It's not something important for the common user.

      I think a lot of people would notice if their laptop suddenly got a third less battery life.

    • by pahles (701275)

      Which insensitive sod has modded parent down?

    • by asdf7890 (1518587)
      Assuming the 18% extra power consumption they found when the machine was idling is representative of what many users will see, than I expect non-power users will notice. If you have a laptop with only two hours of battery life (a netbook from a year or two ago like the AA1 with its standard battery for instance, or many fullsize laptops from a bit earlier) that is a full 21 minutes reduced run time on battery (36 minutes if you count the top, 30%, figure). People using their portable device on a long commut
      • by asdf7890 (1518587) on Friday April 22, 2011 @07:05PM (#35911088)
        And I've just noticed the pun. Somebody mod me "too slow on the uptake".
    • why is this modded troll and not funny?
    • by beelsebob (529313)

      Quite the reverse in fact. Power users care about how much CPU power they can use. Common users care that they can get to $city on the train without their laptop running out of battery.

    • by Osgeld (1900440)

      power or common really doesn't matter, as a common user of a craptop that has to be plugged to the wall anyway, I wouldn't notice.

  • I am probably being extremely naive, but isn't Linus very much against any kind of regression in a major release? If I remember right, some important guy left the project over an argument concerning regression in the package he was maintaining.
    • I don't know--this seems really common with the last dozen kernel releases or so. Power regressions, file system regressions, graphics speed regressions, blah blah blah. With every new kernel release Phoronix reports some serious regressions in various subsystems.
      • by h4rr4r (612664) on Friday April 22, 2011 @06:41PM (#35910900)

        Ever notice it is only Phoronix reporting that?
        When did steam come to linux again?

        Sorry, but I want to see this backed up another source before I just go believing it.

        • by Jah-Wren Ryel (80510) on Friday April 22, 2011 @07:08PM (#35911122)

          Ever notice it is only Phoronix reporting that?

          Do you know of any other organization with a large automated regression testing system for linux kernels? That's not just me being snarky, its a serious question - who else beside phoronix is doing this sort of wide-scale testing on a constant basis?

          • by macshit (157376)

            Do you know of any other organization with a large automated regression testing system for linux kernels? That's not just me being snarky, its a serious question - who else beside phoronix is doing this sort of wide-scale testing on a constant basis?

            I can't answer your question, but Phoronix's testing and benchmarking is notoriously bad, and anything you see there needs to be taken with a gigantic nugget of salt. At best, it's a hint to look around and see if you can find any similar result from a more reputable source.

            • by amn108 (1231606)

              What do you base your criticism of Phoronix on, exactly? At best you draw attention to yourself and not to how bad they are or are not. I've been reading them for a couple of years and even though perhaps they haven't won awards for their journalism or website usability, the information provided SEEMS credible enough and worth a read. Certainly not "notoriously bad" or to be taken with a "gigantic nugget of salt".

              Maybe YOU could build and benchmark a couple of stock kernels on a simple-as-brick Thinkpad T60

              • by Ant P. (974313)

                What do you base your criticism of Phoronix on, exactly?

                How about because they're the Daily Mail of tech news? Did you sleep through the years of bullshit about Steam and UT3? Ever noticed the fact they sound the klaxons five minutes after any minor bug in a 2.6.X-rcY kernel is found? How about the fifty pages of graphs per article just to deliver fifty times as many ads?

                Because that's what it all boils down to: Phoronix only exists for the sole purpose of trolling sites like Slashdot so they can rake in the cash. If I wanted hardware benchmarks there's no short

        • by Anonymous Coward

          Ever notice it is only Phoronix reporting that?
          When did steam come to linux again?

          Wine 0.9.6x, as I recall...

      • by Kjella (173770) on Friday April 22, 2011 @06:53PM (#35911004) Homepage

        Well, what Linus is focused on is breaking user code - if it worked in a released kernel, you will not break it in any future kernel. I don't think there's any strict rule that performance must always be better or power consumption lower. Particularly if you're not doing something "right" and have to add additional checks/locks/synchronization for corner cases that can slow you down, they generally value correctness over performance. That's the case in many of Phoronix' sensationalist news, a development release is very fast but when you make it work 'right' the performance is no longer that impressive. That stuff will happen as close to the bleeding edge as most of the things they report on are. Of course, they do find real regressions too but it's easy to get the wrong impression...

      • Re: (Score:2, Interesting)

        by Anonymous Coward

        I'm on .38 on multiple computers and I'm not seeing these issues, perhaps it's a configuration error on their end (assuming they compile the kernel themsleves for testing) or a configuration error on whatever distribution they test with?

      • Heh, the last ubuntu I ran as my host OS was 10.04 iirc, and it had the intel gfx regression (couldn't even muster the massive overhead of frozen bubble or youtube...
    • by asdf7890 (1518587) on Friday April 22, 2011 @06:34PM (#35910852)
      This is presumably not an intentional regression though, more likely just some new/updated code that is causing the CPU to be more busy when the machine is effectively idle than it was previously. It isn't like someone said "hey, Linus, do you mind if I make the kernel eat more power?"!
      • One would expect that there is some sort of automated performance regression suite that is run regularly (say, daily) to catch offending commits.

        • by asdf7890 (1518587)
          I believe there is a set of automated build loops for the kernel that are used to trap compile time and other non hardware specific errors, but effects such as this one are far harder to automatically detect.
      • My radeon card no longer has functioning power management, as of 2.6.37. It used to be possible to echo dynpm to a sysfs interface and it would downclock the card. That no longer does anything. I did send in the bug to the maintainer, but it apparently is not a high priority item.

        • by asdf7890 (1518587)
          That may lend credence to the theory I guessed at in another post above: a bug may have been introduced that stops certain power management options being detected and enabled.
    • by jimicus (737525)

      Remember that when 2.6 came out, Torvalds himself decided to stop keeping separate stable and development kernel trees. Arguably, there wasn't a lot of point - most Linux distributions add all sorts of patches anyhow, it wouldn't kill them to add another patch here and there if such a regression does come up.

      So now, such a regression does come up occasionally. Doesn't matter if it does - it's not like RedHat or SuSE are going to ship the latest 2.6 kernel without testing and patching where appropriate any

    • The reality of the "No regressions" phrase a bit more complicated. It help tremendously if the regression is noticed during the development stage of the kernel and can be narrowed down to a single patch. Further it also depends on exactly which way you regress - a "can't boot previously working and still supported system" functional regression can be treated differently to a "inserting a new disk is 0.1 of a second slower" performance regression.

  • by Anonymous Coward

    nothing to see here, move along

  • Moronix test suite (Score:3, Interesting)

    by Sene (1794986) on Friday April 22, 2011 @06:57PM (#35911028)
    Would be handy if the suite (or the user) would actually produce graphs with different enough colors to make sense which line is which...
  • by blockhouse (42351) on Friday April 22, 2011 @07:23PM (#35911228)

    Well, that would explain a great deal why my Dell laptop has been overheating and shutting off without warning since that last kernel build. It's shut off three times today and I haven't even done any intensive computing.

    Methinks I need a new box.

    • by bmo (77928) on Friday April 22, 2011 @07:43PM (#35911336)

      >you think you need a new machine

      Either that or open it up and blow out the dust.

      Works wonders for overheating, dontchaknow.

      Cheap/easy fixes first. Always.

      --
      BMO

      • Exactly. I had a Latitude D830 whose CPU was running at a more or less constant 212-218F and was virtually unresponsive. After blasting some canned air into the vent on the sides and back it started working like new.

        I talked to the help desk guys about it and it's a pretty common occurrence with Dell laptops. Seems like a major design flaw to me.

        • by jedidiah (1196)

          > CPU was running at a more or less constant 212-218F

          I have machines with fans either dead or completely removed that don't run that hot.

          • It's what the system monitor reported. I usually run VirtualBox with Windows, NetBeans, JBoss, and run maven builds constantly, so it was pretty busy. I burned my finger when I touched the vent to feel how hot the air was.

        • by drinkypoo (153816)

          My three thousand dollar HP laptop choked itself with dust, too. It's not a problem with Dell laptops. It is a major design flaw. It's not clear what can be done about it.

      • by hey! (33014)

        Granted, but I had the exact same problem crop up yesterday *immediately after upgrading the kernel*. It could be coincidence but if enough people suddenly discover they have to clean out their fan heatsink then there's probably an additional factor at work.

    • by Carewolf (581105)

      You might need to replace the fans. I need to do that every 2 years or so in my latest ThinkPad. It is the only thing that breaks, but it is starting to fail for the second time now, just as the laptop is turning 4. The laptop is still fast enough, so to replace fan or replace laptop?. Fortunately the fan only cost $100 to replace with official spare parts and Lenovo has a nice official online guide on how to do it

  • by masterwit (1800118) * on Friday April 22, 2011 @08:32PM (#35911674) Journal

    Power consumption raised significantly in natty [launchpad.net]
    this is the actual confirmed (4-13) bug report on the Launchpad at least a particular instance.

    Personally I do not run the extra baggage of Ubuntu on my mobile linux device. (netbook)

    When did they start putting unconfirmed or untested bug reports on Slashdot? Sure TFA says much to warrant further investigation... but not to have people like me get curious. (Just my opinion)

    • I may be referring to the wrong distro, oops.

    • by drinkypoo (153816)

      Personally I do not run the extra baggage of Ubuntu on my mobile linux device. (netbook)

      Personally I run ubuntu-minimal on my EEE 701. Best experience I've had with a computer, period, since Jolicloud fucked up their launcher. Everything works, and works flawlessly all the time. I only wish I had a faster machine which worked so well.

  • At least run powertop and compare the output of lspci -vv for each kernel.

  • A little off-topic, perhaps, but how are some of the other *nix's doing in this respect, such as FreeBSD? Is FreeBSD even valid option for a laptop or a netbook?

  • by RichiH (749257) on Saturday April 23, 2011 @03:04AM (#35913154) Homepage

    Phoronix is shit. Pure, grade-A shit. Worthless.

    They have _nothing_ of value to add to anything. Sensationalist crap which is not reported elsewhere, _because it it not an issue_.

    Regressions in the development kernels are part of the process. Even actively trying to avoid Phoronix, I have seen tons of those non-news about some random regression and the breathless follow-up that, lo surprise, they didn't just release but fix the issue. Woooooo!

    Phoronix is shit and it should be blacklisted globally on Slashdot and anywhere else. Stop linking to them, stop commenting on them (other than making others aware of this).

    Rant over.

  • by perotbot (632237) on Saturday April 23, 2011 @10:03AM (#35914460) Journal
    I lost the ability to hibernate my machines in the last few kernels, how about fixing that?

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