iTerm2 being slow after macOS High Sierra update

Thanks for filing an issue! Please answer the questions below so I can help you.

• iTerm2 version: 3.1.2
• OS version: macOS 10.13 17A365
• Attach ~/Library/Preferences/com.googlecode.iterm2.plist here (drag-drop from finder into this window)com.googlecode.iterm2.plist
• Attach a debug log, if possible. Instructions at debuglog.txt
• Are you reporting a performance issue or a hang? Performance issue. Sample_of_iTerm2.txt
• Are you reporting a crash? No.

Detailed steps to reproduce the problem:

1. Open iTerm2.
2. Press enter, scroll in any tab, open menus.

What happened: The entire iTerm2 app is laggy, and also makes the other apps/the system become slower. As soon as iTerm2 is closed, everything goes back to normal. Restarting and First Aid on the disk does not solve the problem. I don't think this is related to the 3.1.2 version, but some incompatibility with the OS.

What should have happened: Everything should be silk smooth like it was in macOS Sierra.

I also just noticed that completely removing iTerm2 and installing again gets rid of the issue. If I set my .plist file back, though, the sluggishness returns.

I see something similar to this as well, I could work around it by reducing the blur radius under preferences->profiles->windows, the very same settings worked fine under Sierra.

Also, when the blur radius is large enough to noticeably decrease performance on a windowed instance of iTerm2 (I typically see this when swiping between spaces), and full screen mode (which has an opaque background, where blur settings should not matter) is activated, performance is still very bad until transparency or blur settings are altered after which it's all fine again (might work with others, I have not tested), even increasing the blur radius works.

I can confirm what Erik says. Deactivating the blur makes iTerm behave as normal. There must be something conflicting with High Sierra.

blur is the issue for me as well on High Sierra

High blur values have always carried a performance cost, but perhaps it's worse now. I guess I should update the UI to warn the user. How far to the right do you guys need to move the slider before it becomes noticeable or bothersome?

changed milestone to %Next Beta

I start noticing it around here.

About here for me:

uname -a
Darwin XXXXXBookPro.local 17.0.0 Darwin Kernel Version 17.0.0: Thu Aug 24 21:48:19 PDT 2017; root:xnu-4570.1.46~2/RELEASE_X86_64 x86_64 i386 MacBookPro12,1 Darwin

I dropped the limit a bit in the latest nightly build (not enough for @ladislas, but around where @jajajaime reports having trouble). Ah, undocumented APIs, how do I love thee