[Webkit-unassigned] [Bug 220150] New: Initial page scroll is slow and laggy for a few seconds, after browser has been idle

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=220150

            Bug ID: 220150
           Summary: Initial page scroll is slow and laggy for a few
                    seconds, after browser has been idle
           Product: WebKit
           Version: WebKit Local Build
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: Major
          Priority: P2
         Component: UI Events
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dave at grow.game

I am using WebKitGTK 2.30.4 on my own "from scratch" Linux distro, with a one-source-file browser written in C. Very basic usage of WebKit, nothing special. Everything about the browser works great, except for one rather annoying problem. If the browser has been allowed to idle for about 20-30 seconds, initial scrolling of a page will be slow and laggy. After a couple seconds of intense scrolling, it "clears up" and becomes smooth and responsive, and will remain so up indefinitely--until the browser is allowed to idle again, at which point the problem reoccurs. 

Literally every other program on this computer is blazing fast and responsive, because I have specifically built this system to be so. Chromium for example is fast and snappy. This is a Ryzen3 with 32GB of ram, an SSD, and no swap partition. So I'm pretty sure it's not the OS. Only WebKit has this problem.

In an attempt to triage this, I've recompiled WebKit with virtually everything disabled (particularly OpenGL support), with no effect. I thought it might be a problem with some thread being given too low priority, so I also tried disabling functions relating to setting thread priority, and increasing various priorities in ./Source/WTF/wtf/glib/RunLoopSourcePriority.h, with no apparent effect.

So now I turn to you, dear WebKit bugzilla, in hopes of finding a solution to this very frustrating problem. 

Hopefully this is a known issue and you might have some ideas on how to solve it. If not, I have a full suite of debugging tools available, so let me know what steps I can take to help diagnose and solve this problem. 

Here's how WebKit is configured right now. Compiler is GCC 9.3.0, on glibc 2.27, with Linux 4.18.5. Let me know if you need any more info:

cmake -DCMAKE_INSTALL_PREFIX=/usr \
      -DCMAKE_BUILD_TYPE="RelWithDebInfo" \
      -DCMAKE_CXX_FLAGS="$CXXFLAGS" \
      -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
      -DENABLE_ACCELERATED_2D_CANVAS=OFF \
      -DENABLE_ASYNC_SCROLLING=ON \
      -DENABLE_BUBBLEWRAP_SANDBOX=OFF \
      -DENABLE_DRAG_SUPPORT=ON \
      -DENABLE_GEOLOCATION=OFF \
      -DENABLE_GRAPHICS_CONTEXT_GL=OFF \
      -DENABLE_GTKDOC=OFF \
      -DENABLE_MEDIA_SOURCE=OFF \
      -DENABLE_MHTML=ON \
      -DENABLE_MINIBROWSER=OFF \
      -DENABLE_NOTIFICATIONS=OFF \
      -DENABLE_ORIENTATION_EVENTS=OFF \
      -DENABLE_SPELLCHECK=OFF \
      -DENABLE_TOUCH_EVENTS=OFF \
      -DENABLE_UNIFIED_BUILDS=ON \
      -DENABLE_VIDEO=OFF \
      -DENABLE_WEB_AUDIO=OFF \
      -DENABLE_WEBDRIVER=OFF \
      -DENABLE_WEBGL=OFF \
      -DENABLE_WEBASSEMBLY=OFF \
      -DENABLE_WEB_RTC=OFF \
      -DENABLE_X11_TARGET=ON \
      -DPORT=GTK \
      -DUSE_LIBNOTIFY=OFF \
      -DUSE_SYSTEMD=OFF ..


Thanks for any help you can provide!

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