https://bugs.kde.org/show_bug.cgi?id=515887
Bug ID: 515887
Summary: [Feature request] Run heavy tasks in dedicated threads
to prevent stutters and freezes
Classification: Plasma
Product: kwin
Version First 6.5.5
Reported In:
Platform: Other
OS: All
Status: REPORTED
Keywords: efficiency-and-performance, wayland-only
Severity: wishlist
Priority: NOR
Component: performance
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Currently kwin_wayland does almost all tasks synchronously in the main thread,
which is an issue in term of performances especially when kwin loads things
such as effects at runtime, or interacts with clients that give heavy tasks to
the compositor. As a Plamsa-Wayland user, I see to many scenario where kwin
drop frames, including the mouse cursor even if hardware cursor is enabled.
It’s very noticeable on a high refresh rate monitor.
Examples of freezes:
- Alt-tabbing is causing micro-freezes, because kwin is stall during the load
of the animation effect. https://bugs.kde.org/show_bug.cgi?id=479250.
- Applications such as Gimp which set the cursor shape every frame can
slowdown kwin and causes frame drops at high refresh rate.
https://bugs.kde.org/show_bug.cgi?id=506240.
- Applications which are not GPU accelerated slowdown kwin because the
framebuffer is copied from CPU to GPU synchronously in the main thread of the
compositor. https://bugs.kde.org/show_bug.cgi?id=513295.
These performance issues happens only in a Wayland sessions. With Xorg, a least
the cursor is always smooth.
Here is a proposal of the thread architecture:
- A dedicated thread for input management and cursor position.
- A dedicated thread for the kwin render.
- A thread pool to manage threads for applications interactions, effects and
other heavy tasks.
- A KMS thread (already implemented).
- A dedicated thread for window management.
- The main thread should only be used for kwin initialization/termination and
thread management.
I know all of that is hard to implement and can’t be implemented straight away,
but this is just to give an idea to how I see performance issues in
kwin_wayland and I hope my advice will help KDE developers to improve kwin
which is an incredible project.
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