

Phoronix successfully git-bisects Linux power regressions for ~15% improvement - sandGorgon
http://www.phoronix.com/scan.php?page=article&item=linux_2638_aspm&num=1

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ChuckMcM
I'll save you time and the amazing cat and mouse game of trying to move your
mouse around that site without it popping up a half dozen advertisements ...
(oh and its a giant advertisement for the Phoronix product)

Power management sucks. Hardware vendors don't care that it sucks on Linux,
they only care that it works on Windows. Microsoft pays people to make sure it
works on Windows and browbeat manufacturers to make it work and they program
around it on every platform where it doesn't work.

In the 2.6.38 kernel a change was comitted into the mainline sources which
chose 'probably works' over 'randomly hangs.' The fix was to stop trying to do
power control and that means longevity is shorter (sometimes much shorter)

Linux has maybe three people total (if you could somehow add up all the
fractional people who care enough about this to work on it) who both
understand how the latest invocation of power management works, and care
enough to fix it for their system.

Sometimes their fixes get into mainline, sometimes they live on some out of
the way branch because someone on LKM didn't like them, sometimes you have to
write to them to find out what they did. If you don't have a system where one
of these fractional people made it work, you're screwed.

This is the life you chose when you use Linux.

This is true for lots of things Linux. I would love to help fix it (the fact
that Linux sucks in the corners that aren't sexy) I don't know how yet. I'm
open to suggestions. Google could do this (they use Linux on laptops) but they
would only fix it for the corporate model/rev not for everything.

~~~
sandGorgon
To be fair to Michael (the founder of Phoronix) - he did spend a large amount
of time and resources building out the PTS and integrating it with power-
measurement devices that let him automatically narrow down this commit.

Personally, if it helps me wring more battery life out of my laptop, I would
considered the ads (or the donation) well-suffered.

~~~
adobriyan
[http://marc.info/?l=linux-
kernel&m=127535359014939&w...](http://marc.info/?l=linux-
kernel&m=127535359014939&w=4)

    
    
      On Tue, Jun 1, 2010 at 10:46 AM, Alex Buell <alex.buell@munted.org.uk> wrote:
      > On Mon, 2010-05-31 at 17:39 -0600, Robert Hancock wrote:
      >> On 05/31/2010 05:19 PM, Alex Buell wrote:
      >> > http://www.phoronix.com/vr.php?view=14976
      >> >
      >> > Question: Why?
      >>
      >> Good question.. I guess it would too much to ask of them to try to
      >> figure out what area the problem lies in (even to the point of figuring
      >> out if it's a CPU or IO-bound problem), or try to bisect, or at least
      >> report it to LKML before going to the trouble of creating 5 pages of
      >> graphs.. Given the 20x slowdown in some of the benchmarks you'd think it
      >> wouldn't be too hard to narrow down.
      >
      > What I really don't get is why they didn't talk to people on
      > linux-kernel before posting those claims on phoronix. :S
      
      Well thats kinda obvious, its "journalism" in the days of google
      adwords. They make revenue by making people click on their website,
      they don't make money being useful or interacting with others.
      Phoronix in all the years I've been dealing with them as the only
      place doing any reporting on graphics, have never once confirmed a
      source, asked for information directly or anything you'd expect from
      real journalists, again because that doesn't drive page hits, whereas
      sensationalist useless headlines are the main point of the site.
    
      Dave.

~~~
rmc
Interest poit of view of the authors intent. But the hell with that, we're
hackers. Does it work?

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kleiba
A little bit ironic, if I understand the article correctly: Linux disables
power management when the BIOS claims not to support it. But a lot of BIOS'es
are misconfigured (intentionally) because otherwise Windows' power management
wouldn't work. So, Linux - in trying to do things right - suffers indirectly
from Windows' disabilities.

~~~
FooBarWidget
A lot of hardware problems on Linux are like this. Unfortunately everybody
still blame Linux.

~~~
eropple
As well they should. _De facto_ standards, in this case Windows, are no less
real than _de jure_ ones.

It sucks and it's unfair, but if you want compatibility, you target what
exists.

------
sandGorgon
see if your laptop is affected - add "pcie_aspm=force" to your boot
parameters. Ubuntu bug (updated) here -
<https://bugs.launchpad.net/ubuntu/+source/linux/+bug/760131>

------
kevinburke
So bisect only helps you find the commit that caused the regression, not the
source code problem that caused the error?

~~~
Tuna-Fish
Yes, but because the best practise in git is to make commits very small, the
commit that caused the regression is typically ~= the source code problem that
caused the error.

