Re: Very bad performance from intel chipset on Thinkpad T540p (2880x1620)

From: Dave Gordon <david.s.gordon@intel.com>
To: Marc MERLIN <marc_xorg@merlins.org>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	intel-gfx@lists.freedesktop.org
Subject: Re: Very bad performance from intel chipset on Thinkpad T540p (2880x1620)
Date: Tue, 28 Apr 2015 08:35:21 +0100	[thread overview]
Message-ID: <553F3839.4010600@intel.com> (raw)
In-Reply-To: <20150424161836.GC30934@merlins.org>

On 24/04/15 17:18, Marc MERLIN wrote:
> On Fri, Apr 24, 2015 at 04:53:53PM +0100, Chris Wilson wrote:
>> Whether of not it tears depends upon your window manager. On bare X,
>> using mplayer -vo xv or -vo gl, should not tear. Under a compositing
>> window manager, it depends upon how it decides to update the screen. To
>> force everything to update without tearing, use
>>
>> echo > /etc/X11/xorg.conf.d/90-intel.conf <<EOF
>> Section "Device"
>> 	Identifier "igfx"
>> 	Option "TearFree"
>> EndSection
>> EOF
> 
> Cool, thanks for the tip and your help.
> 
> I was curious to see how my power use would be, and got about the same power
> use at idle with LCD to minimum:
> The battery reports a discharge rate of 12.4 W
> The estimated remaining time is 7 hours, 27 minutes
> 
> Summary: 171.5 wakeups/second,  0.1 GPU ops/seconds, 0.0 VFS ops/sec and 2.0% CPU use
> 
> Power est.              Usage       Events/s    Category       Description
>   3.73 W      1.9%                      Device         Display backlight
>   1.16 W      4.7 ms/s      65.3        Process        [btrfs-transacti]
>   741 mW      0.9 ms/s      41.9        Interrupt      [4] block(softirq)
>   175 mW    156.0 µs/s       9.9        Process        [rcu_sched]
> 
> 
> Then, if I turn my screen off (backlight 0), it actually seems to save another 7W:

On many small devices (phones, tablets, notebooks, modern laptops) the
backlight consumes about as much as everything else put together! So #1
energy-saving tip is always "turn the brightness down" followed by "turn
the screen off at every opportunity".

.Dave.

> The battery reports a discharge rate of 5.06 W
> The estimated remaining time is 18 hours, 5 minutes
> 
> Summary: 79.4 wakeups/second,  0.2 GPU ops/seconds, 0.0 VFS ops/sec and 1.8% CPU use
> 
> Power est.              Usage       Events/s    Category       Description
>   229 mW      1.4 ms/s      13.4        Process        [btrfs-transacti]
>   181 mW      4.1 ms/s      10.4        Process        /usr/bin/enlightenment
>   174 mW    206.2 µs/s      10.2        Interrupt      [4] block(softirq)
> 
> 
> So the good news is that the driver sems to do fine on batteries with the
> default options now.
> 
> Thanks,
> Marc

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