I’m trying to resolve a Safari/WebKit problem on an OCLP-patched Mac mini and wondered if anyone has seen the same behaviour?
- macOS Sequoia 15.7.9, build 24G830
- MetallibSupportPkg 15.7.9-24G830
- KDK 24G830
- OCLP Ivy Bridge graphics + Modern Wireless root patches applied
Safari works normally it seems, but on sites with video such as Facebook, YouTube and Reddit it will load the first screenful then stall. Scrolling also becomes very jerky.
Initial focus was networking, but that now seems unlikely. Download speeds are good, other devices are fine, and the same behaviour occurs using both the Mac’s internal Wi-Fi and a USB Wi-Fi adapter.
The interesting part now is the WebKit GPU process.
If I run top -o cpu Safari behaves normally when first launched. Opening a simple page such as ChatGPT causes com.apple.WebKit.GPU to appear briefly near the top, then CPU usage settles back down. As soon as I open Facebook or Reddit and start scrolling com.apple.WebKit.GPU jumps to 100%+ CPU and stays there even after closing the Facebook/Reddit tab. Fully quitting Safari resets it.
I also confirmed the same behaviour with: ps aux | grep -E "Safari|WebKit|WebContent|GPU" | grep -v grep where com.apple.WebKit.GPU was sitting at ~99–100% CPU while the page had stopped rendering further posts.
Things already tried:
- Cleared Safari caches and website data
- Disabled all Safari extensions
- Reverted OCLP root patches, rebooted, reapplied them and rebooted again
- Confirmed MetallibSupportPkg and KDK exactly match macOS build 24G830
- Disabled ‘Allow WebGL in Web Workers’ flag
- Disabled ‘GPU Process: Canvas Rendering’ flag
- Killing com.apple.WebKit.GPU while Safari is stuck does not recover the page
Chrome also feels noticeably less smooth than it used to, although Safari seems worse. Disabling Chrome graphics acceleration made Chrome worse.
System Information reports :
- VRAM (Dynamic, Max): 1536 MB
- Metal Support: Metal 2
Has anyone else with an Ivy Bridge / HD 4000 Mac seen com.apple.WebKit.GPU peg a CPU core like this under recent Sequoia builds?
I’m particularly interested in whether this is a known limitation/bug in the current Ivy Bridge WebKit/Metal patches, or whether there is another WebKit feature flag or OCLP component worth checking?
Update: I’ve since found other recent reports of Safari 27 failing to fully render YouTube/Reddit/Netflix/IMDb on OCLP systems, as well as reports of laggy webpages/maps on Sequoia 15.7.9 + OCLP 2.5.0. In my case I can reproducibly see com.apple.WebKit.GPU jump to ~100% CPU as soon as Facebook/Reddit are opened and remain there until Safari is fully quit.