So it seems like the issue is a combination of:
1. Unity8 using a zero swap interval (somehow, by accident?)
2. Unity8 taking around 10ms to render each frame -> 100Hz
3. USC can only take one frame every 16.6ms (60Hz), so will drop half of what
Unity8 produces.
This yields only 50Hz output to the screen, which is roughly only every
second frame from Unity8 reaching the screen, on an interval that's out
of phase with the screen. So that's the stuttering.
** Changed in: mir
Milestone: 0.26.1 => 1.0.0
** Changed in: mir
Status: New => In Progress
** Also affects: mir/0.26
Importance: Undecided
Status: New
** Changed in: mir/0.26
Importance: Undecided => High
** Changed in: mir/0.26
Status: New => Confirmed
** Changed in: canonical-devices-system-image
Status: New => Confirmed
** Changed in: mir/0.26
Milestone: None => 0.26.1
** Changed in: mir/0.26
Assignee: (unassigned) => Daniel van Vugt (vanvugt)
** Description changed:
- Unity8 stutters constantly (like half frame rate) on an i7 desktop.
+ Unity8 stutters constantly (like half frame rate) on a high-end desktop.
This regression only happened recently, perhaps due to the introduction
of Mir 0.26.0.
Surprisingly though, using the same Mir release I can start a demo
server on another VT and everything is silky-smooth. The problem only
seems to occur with Unity8.
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https://bugs.launchpad.net/bugs/1661128
Title:
[regression] Unity8 stutters constantly (like half frame rate)
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