QtWebEngine loads very slowly

Geremia · 04-27-2021, 12:56 PM

I'm experience incredibly slow loading times for QtWebEngine, which causes Calibre's ebook-viewer several seconds just to load a simple, small EPUB. From MobileRead forum:

Code:

$ QTWEBENGINE_CHROMIUM_FLAGS="--disable-gpu --enable-logging=stderr --v=0" calibre-debug -w *.epub

[0.000] Load of book started
[0.005] prepared emitted
[0.232] webview loading requested
[3.239] bridge ready
[5.279] loading finished
Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 196.0 x 196.0
physicalDpi: 162.56 x 161.36470588235292
Using calibre Qt style: True

Qt 5.15.2
KDE Frameworks 5.81.0
KDE Plasma 5.12.4

Graphics card: NVIDIA GK208B [GeForce GT 710], Nouveau driver

floppy_stuttgart · 04-28-2021, 09:34 AM

this? https://www.qtcentre.org/threads/628...extremely-slow
this? https://forum.qt.io/topic/52360/qweb...ry-very-slow/4

Geremia · 05-01-2021, 01:32 PM

Quote:

Originally Posted by floppy_stuttgart

this? https://www.qtcentre.org/threads/628...extremely-slow
this? https://forum.qt.io/topic/52360/qweb...ry-very-slow/4

I don't think so. I don't get slow performance once the contexts, which take several seconds to initialize, get setup.

Code:

QTWEBENGINE_CHROMIUM_FLAGS="--enable-logging --log-level=0 --v=1" calibre-debug -w *.epub

Grepped relevant lines:

Code:

Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 1
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 1
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 2
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 2
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 3
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 4
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 5
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 6
Num tracked contexts: 5
Num tracked contexts: 4
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 5
Destroyed context for extension
Destroyed context for extension
Destroyed context for extension
Destroyed context for extension
Created context:
  effective context type: WEB_PAGE
Created context:
  effective context type: UNSPECIFIED
Num tracked contexts: 6