Stellarium performance regression (visibly stuttering)

[Daniel van Vugt]

I have two identical Xeon desktops with identical monitors. They are running different software:

Ubuntu 16.04: stellarium 0.14.3-1 --> smooth
Ubuntu 17.10: stellarium 0.16.0-1 --> stutters

On both machines when I drag the sky the counter at the bottom of the screen shows 59-60 FPS. However on the latter machine the picture stutters visibly (like it's really 30FPS/20FPS/15FPS).

It doesn't seem to matter whether I use Xorg or Wayland, Gnome Shell or Unity7. The stuttery result is the same. I've tried other OpenGL apps and none of them seem to have this problem. Only Stellarium 0.16.0.

[Daniel van Vugt (vanvugt)]

Possibly bug 1661375?

[Alexander Wolf (alexwolf)]

Could you try version 0.16.1 on Ununtu 17.10?
--
With best regards, Alexander Wolf.

[gzotti (georg-zotti)]

It's quite likely not that bug.

However, "Xeon" means almost nothing. Like "Pentium", it can also be 10 years old. As always, your logfiles would give indication about graphics hardware (which really matters), drivers, etc.

[Daniel van Vugt (vanvugt)]

Well, I've been doing GL development on these machines [1] for a few years. I know what they're capable of and that 60Hz should appear smooth and not stuttering. Not to mention the identical machine next to it running Stellarium 0.14 is perfectly smooth still...

Which log files exactly would you like?

[1] https://ark.intel.com/products/80916/Intel-Xeon-Processor-E3-1246-v3-8M-Cache-3_50-GHz

[Alexander Wolf (alexwolf)]

Please show ~/.stellarium/log.txt

[Daniel van Vugt (vanvugt)]

Here it is. Not much to see.

[gzotti (georg-zotti)]

We would be interested in the part that follows. Something like

=================================================================
 -------------------------------------------------------------------------
[ This is Stellarium 0.90.0.9918 [stellarium] - http://www.stellarium.org ]
[ Copyright (C) 2000-2017 Fabien Chereau et al. ]
 -------------------------------------------------------------------------
[...]
OpenGL supported version: "4.5.0 NVIDIA 385.41"
[...]
Detected: OpenGL "4.5"
Driver version string: "4.5.0 NVIDIA 385.41"
GL vendor is "NVIDIA Corporation"
GL renderer is "GeForce GTX 960M/PCIe/SSE2"
GL Shading Language version is "4.50 NVIDIA"
GLSL Version Number detected: 4.5
GLSL version is fine, we should not see a graphics problem.
======================================================================

In any case, Intel HD graphics is not the fastest.

[Daniel van Vugt (vanvugt)]

I don't get any of that information. Even tried "--dump-opengl-details" and get nothing other than what's shown in comment #6.

Just tried env LIBGL_SHOW_FPS=1 though, and it agrees with Stellarium and prints "FPS = 60.0". But what I see on screen is not 60Hz. It's stuttery like 30Hz/20Hz/15Hz.

So it sounds like either:
 (a) A lower level compositing problem (but why is it consistent between shells and Xorg/Wayland?); or
 (b) Stellarium really is flipping 60 frames per second but they're not actually unique frames.

I'll debug this myself some time, when I have time. Unless anyone can make some suggestions.

[gzotti (georg-zotti)]

Some Linux systems have Qt logging largely disabled.

A bit of googling around brought me to sites like
https://bugzilla.redhat.com/show_bug.cgi?id=1227295

from which I wrote a summary
https://github.com/Stellarium/stellarium/wiki/FAQ#Logfile_has_no_details

Maybe this helps.

[Alexander Wolf (alexwolf)]

Could you disable Satellites plugin and check it again?

[Daniel van Vugt (vanvugt)]

I've now changed hardware and software.

Using Ubuntu 18.10 (development) with stellarium 0.18.0-1 I can't reproduce any bug.