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From: Sean V Kelley <sean.v.kelley@intel.com>
To: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jon Kristensen <info@jonkri.com>
Subject: Re: i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013)
Date: Thu, 28 Aug 2014 09:41:20 -0700	[thread overview]
Message-ID: <CA+qSnqj9Cr8-Wh_Pb=uREL4wkoa9e4X7TL_9+Oz4LEzT3nTE1Q@mail.gmail.com> (raw)
In-Reply-To: <87sikklvhu.fsf@intel.com>


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On Mon, Aug 25, 2014 at 3:22 AM, Jani Nikula <jani.nikula@intel.com> wrote:

>
> [just moving from lkml to intel-gfx for a better fitting audience]
>
> On Mon, 25 Aug 2014, Jani Nikula <jani.nikula@intel.com> wrote:
> > On Fri, 22 Aug 2014, Eric Rannaud <eric.rannaud@gmail.com> wrote:
> >> Hi,
> >>
> >> Between 3.15.4 and 3.15.8, there was an increase in idle power
> consumption on
> >> Apple Macbook Pro 15 (late 2013) on a freshly booted system (no wifi
> driver
> >> loaded; brightness set to 4/100; X running; no desktop environment,
> except
> >> Awesome), from 6.5W to about 10.5W, as reported by powertop.
> >>
> >> In the stable tree, it bisects to:
> >>         commit f4db98240ac2c6d9d2118c6f82d483ff5293f1ed
> >>         Author: Chris Wilson <chris@chris-wilson.co.uk>
> >>         Date:   Fri Jun 6 10:37:11 2014 +0100
> >>
> >>             drm/i915: Disable FBC by default also on Haswell and later
> >>
> >>             commit 0368920e51ae0cded0eb518c340a4dd17764d461 upstream.
> >>
> >>             It causes black screen on bootup and is approximately 100x
> >> slower than
> >>             running with FBC disabled, so the GPU runs at a high
> >> frequency for much
> >>             longer - completely contrary to the power saving claims.
> >> It also still
> >>             has mutex deadlocks in multi-head scenarios, which can lead
> to a
> >>             system/X lockup. These bugs were known before FBC was
> >> enabled by default
> >>             on Haswell and still have not been fixed.
> >>
> >> The issue is still present in Linus' tree (v3.17-rc1-22-g480cadc2b7e0).
> >>
> >> With a 75Wh battery, that's a significant loss in battery life in
> normal use.
> >>
> >> I'll be happy to help test any potential fix.
> >
> > The earlier regression trumps, and in this case it was enabling FBC by
> > default on Haswell. Sorry.
> >
> > You can enable FBC with i915.enable_fbc=1 module parameter, but all bets
> > are off. See the commit message you quoted above. I don't recommend.
> >
>


For what it's worth, I have a Mid-2014, Macbook Pro Retina (13inch
display), running Archlinux with 3.16.

Definitely, enable_fbc is a win for me and I do manually enable it.  But I
am still seeing what I believe to be
a regression overall of about +4W even with fbc enabled.  Still digging for
clues.

Sean





-- 
Sean V. Kelley <sean.v.kelley@intel.com>
Open Source Technology Center / SSG
Intel Corp.

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_______________________________________________
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  parent reply	other threads:[~2014-08-28 16:41 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-22 17:40 i915: Regression: +4W in idle power use on Macbook Pro 15 (late 2013) Eric Rannaud
2014-08-25 10:19 ` Jani Nikula
2014-08-25 10:22   ` Jani Nikula
2014-08-25 12:19     ` Eric Rannaud
2014-08-26 11:06       ` Ville Syrjälä
2014-08-26 13:38         ` Eric Rannaud
2014-08-26 14:57           ` Eric Rannaud
2014-08-26 20:59             ` Daniel Vetter
2014-08-26 23:00               ` Eric Rannaud
2014-08-27  9:17                 ` Ville Syrjälä
2014-08-27 17:50                   ` Eric Rannaud
2014-08-28 20:08                 ` Lu, Ran
2014-08-28 16:41     ` Sean V Kelley [this message]
2014-08-28 17:19       ` Eric Rannaud

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