[Bug 102963] New: Choppy gnome desktop animations under linux 4.13.x (since 4.12.x)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102963

            Bug ID: 102963
           Summary: Choppy gnome desktop animations under linux 4.13.x
                    (since 4.12.x)
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: harish.hyma at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Specs:
Thinkpad X250
CPU Model name: Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz (Broadwell?)
Intel HD 5500 graphics
8Gb RAM

I have recently upgraded from 4.9.51 LTS kernel to 4.13.3 downloaded from
kernel.org. By doing this, I had noticed that the gnome animations have become
visibly poorer in quality due to choppiness. This was not the case under
linux-4.9.51-LTS. The somewhat choppy animations can be visibly seen when
closing/opening applications such as the gnome-terminal. 

I tried to narrow down which kernel caused this problem. My investigation led
to a culprit commit that happened between 4.11.9 and 4.12.1 kernels. If I have
to go by logic, since this a graphics problem, I suspect that it is a drm/i915
commit. 

I do not see further drm/i915 commits from 4.11.9 to 4.11.13, so I can safely
rule out that the culprit must be somewhere between 4.12 rc1 and 4.12.1. There
are just too many commits between the two versions for me to tell which version
is responsible for this.

To rule out possible bad .config settings, I used the .config parameters of my
4.9.51-LTS kernel (which I know is not causing choppy gnome animations) to
build 4.12.1 kernel.

I have no knowledge on how to bisect kernels since I am an average everyday
desktop user. I also do not have enough computational resources/time. However,
I felt the urge to report this issue as many people have been complaining about
poor gnome animation performance and this could be *one* of the reasons why.
The bad commit would unfortunately propagate down to the future 4.14 LTS kernel
release if it is not found. Therefore I am reporting this to at least let
people know this issue exists.

I believe this is a case of graphics regression of the kernel and not the Gnome
Desktop since the only constant variable here is the Gnome Desktop. If not,
maybe the graphics stack actually evolved to become better and Gnome Desktop is
not able to properly utilise the new changes? I do not know since I am not an
advanced user. 

In the coming days I will *try* to compile/build the 4.12.x kernel if I have
time, starting from rc1 to try to find the offending version, but it would
really help if anyone else out there would report on this too.

In the meanwhile, please advice what to do? Thank you in advance.

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