Hello, is there a way to limit Karma's threads to all but one?
I saw other similar posts but it seems this control was moved somewhere else?

Under the tab 'Output' of the usdrender rop there is a parameter 'Maximum Threads' you can tick on.

Read the tool tip so you can set with a positive or negative number according how you want it specified.

BabaJ
Under the tab 'Output' of the usdrender rop there is a parameter 'Maximum Threads' you can tick on.

Read the tool tip so you can set with a positive or negative number according how you want it specified.

Thank you, but which one is it for—the live preview in the viewport or the final render? I’m looking for the one that controls live previews in the viewport

It's for where ever you have set on the render rop - 'Render to Disk', 'Render to MPlay' or 'Render to Disk in Background'.

I don't think there is such control for the viewer rendering as it is part of the application(Houdini).
As such resources like CPU is controlled/delegated by the OS.

I see, thanks, sometimes Karma uses 100% CPU and it just freezes until it's done. I wonder if there is something we can do, ESC does nothing, in Mantra we could stop the render using ESC for ex

If under the drop down menu that you normaly choose a view and/or Karma CPU/XPU Storm etc., there is a side menu 'Render Settings'.
If you select 'Viewport Settings'....then bring up the Display Options:solaris panel with spacebar +D.

Then under the Render Tab select Karma CPU from drop down 'Show options for'.

Under another tab 'Basic' there is an 'IPR Reserve Threads' that might help you.

This is strange to me, I always thought IPR 'stuff' was part of the Mantra frame generation but not Solaris(usd).

But...it might be worth giving it a try as it is under Karm CPU options and not greyed out.