[Intel-gfx] Very bad performance from intel chipset on Thinkpad T540p (2880x1620)

[Chris Wilson]

On Thu, Apr 23, 2015 at 05:31:01PM -0700, Marc MERLIN wrote:
> Hi Chris, thanks for the answer,
> 
> On Thu, Apr 23, 2015 at 11:49:24PM +0100, Chris Wilson wrote:
> > On Thu, Apr 23, 2015 at 03:22:44PM -0700, Marc MERLIN wrote:
> > > I do boot my kernel with these options I found recommended to save
> > > power, maybe I should remove some of them because they kill performance?
> > > pcie_aspm=force i915.i915_enable_rc6=7 i915.i915_enable_fbc=1 i915.semaphores=1 i915.lvds_downclock=1 acpi_backlight=vendor
> > 
> > Those options are broken.
>  
> Ok, which ones specifically? :)
> Without some of those, battery use from the driver has been bad in the past,
> but I don't know which one does what exactly :)
> 
> - pcie_aspm=force

Probably saved your battery life, though the kernel should now be fixed.

> - i915.i915_enable_rc6=7

Broken, unvalidated mode for your hardware.

> - i915.i915_enable_fbc=1

Buggy. Can be very slow, causes GPU hangs and machine lockups.

> - i915.semaphores=1

Default.

> - i915.lvds_downclock=1

Subject to visual bugs.

Setting (almost) any of the i915 options will taint your kernel (i.e.
mark it as being in a known broken state).

> > > Relevant bits form Xorg.log:
> > > [    49.114] (II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so
> > > [    49.122] (II) Module intel: vendor="X.Org Foundation"
> > > [    49.122] 	compiled for 1.15.99.904, module version = 2.21.15
> > 
> > Start by grabbing an updated xf86-video-intel.
> 
> On debian testing and unstable, it's the latest:
> legolas:~# apt-get install xserver-xorg-video-intel/unstable
> Reading package lists... Done
> Building dependency tree       
> Reading state information... Done
> xserver-xorg-video-intel is already the newest version.
> Selected version '2:2.21.15-2+b2' (Debian:testing [amd64]) for 'xserver-xorg-video-intel'
> 
> But now that you mention it, I just found this, so I'll try this out:
> legolas:~# apt-get install xserver-xorg-video-intel/experimental
> Reading package lists... Done
> Building dependency tree       
> Reading state information... Done
> Selected version '2:2.99.917-1~exp1' (Debian:experimental [amd64]) for 'xserver-xorg-video-intel'
> 
> On top of being bleeding edge enoug not to be in debian unstable, does it have 
> performance enhancements that you are hopeful will help my situation?

Lots.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre