[Bug 101259] General artifacs shortly after CPU warming up

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101259

--- Comment #9 from liang <clamfly at sina.com> ---
I may have the same issue, here's my findings.

1. Strange "short line" patterns in some Qt5 apps' menu.
I took a screenshot, see attachment. The height light effect of a selected menu
entry rendered partialy, and previous selected entry also partialy redraw. This
can be reproduced consistently, each time I boot, start the DE, launch only one
Qt app and move the mouse over the menu for some time, it comes.
Affected apps including those in the qt5-tools package: Qt Assistant, Qt
Linguist ... I am on a Qt5-Gtk2-Gtk3-mixed environment, only the Qt side
affected.
I also notice that these "short lines" are based of 16-pixel length, they are
vey similar to the cache-coherence-failure patterns I've known in the old-day
ARM device. My display is 32-bit-color depth, so each "short line" is 64-byte,
which is same as the CPU cache-line size I found in /proc/cpuinfo.

2. The vanish speed of artifacts seems relate to CPU/RAM load.
I notice that under a light load, in above test, those "short line" vanish very
slowly (almost still), and if I run mprime torture in the background (blend
tests, all thread, rw lots of RAM), they just vanish instantly.

3. Artifacts in chromium while browsing some long text page, just as
Francisco's.
These artifacts vanish quickly if I stop scrolling, also, I notice that
chromium makes some CPU laod while scrolling.

4. Some demos of the PixiJS project also have the "short lines"
PixiJS is a 2D library over WebGL: https://github.com/pixijs/pixi.js
You can launch the demo directly from their README.md page in your browser.
The affected demos I've tried were "WebGL Filters!" and "Run pixie run". It's
very obvious and consistent, those "short lines" stick around every moving
object.
The background mprime torture also affect this a lot, the "noise" became much
less.

5. Switch back to the intel Xorg DDX driver (xf86-video-intel) solved it some
extent.
I use modesetting driver currently, and Arch recommends that. To catch some
hope, I changed it back to the intel DDX driver and did some quick test, it
seems none of above can be reproduced. But rolling back to intel DDX also bring
back all the problems I encountered before: slow respond, tears, hangs ...

6. Rolling back to mesa-17.0.5 has some improvement.
Only quick test:
    The Qt5 menu patterns, can't reproduce.
    Chromium with long text page, seems no artifact.
    However, PixiJS demos still have some noise, but much less than 17.1.4.
It seems that rolling back makes it harder to reproduce.
BTW, PixiJS demos now have a lot of tears, it may also exists in 17.1.4,
covered by the heavy "short line" noise.


my config:
hardware     : Skylake i7-6700 (HD530), 32GiB RAM (dual-channel)
distribution : Arch Linux, with almost up-to-date packages
kernel       : 4.11.9-1
xorg-server  : 1.19.3-2  (use modesetting driver instead of intel DDX)
mesa         : 17.1.4-1
DE           : Xfce 4.12

Hopes the above helps.

Francisco, would you please try the Qt5 menu or the PixiJS demos? If they
behave the same, then I'm sure I'm on a right BUG report. It may also help your
bisecting a bit.

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