wow 11.1 let's us see the addons CPU usage, and i noticed that IceHUD is taking too much CPU.
screenshot 1 is made on epic BG Isle of the Conquest, i'm out of combat standing far away from the main fight.
screenshot 2 is made when i attack pvp dummy.
i also noticed that IceHUD's RAM usage is increasing even if i do nothing, it grows unit 30 megs and then drops to 6 megs, then repeat.
during the test, i disabled all addons except IceHUD.
IceHUD Version: v1.15.12

There's not much actionable for me here, unfortunately. The mod is going to use more resources the more modules are enabled and tracking things, by nature. You can go into the settings and scale back how often it's allowed to update if you aren't happy with the CPU usage, but an average usage of 2% doesn't seem like much of a problem to me.
As for memory rising and resetting: that's called Garbage Collection. Mods will use memory for something, then not need it any more, and the game will eventually recapture that memory.

At any rate, I haven't noticed specific hot spots in the mod that can be addressed, so at this time I'd recommend either using the update rate slider in the settings or discontinuing the use of IceHUD if it's not performant enough for your needs.

thank you for the answer
i tried changing update interval, looks like it does not have any influence at all.
i also use ThreadPlates and WeakAura and they never use more then 1% CPU, usually 0.2-0.5%, i tried ShadowedUnitFrames instead of IceHUD and it also uses very little CPU time 0.1-0.2%
but i like IceHUD and been using it since Cata
i need a better PC i guess

Is your game actually suffering because of it? 98% CPU available to the game does not seem like it would be much of a problem.

I'm sure there are ways to improve IceHUD's performance, but I don't play the game much anymore to spend time looking into it.

If you identify a specific module that has a high impact (usage lowers when it's disabled), let me know and I can dig in further.

Is your game actually suffering because of it? 98% CPU available to the game does not seem like it would be much of a problem.

I'm sure there are ways to improve IceHUD's performance, but I don't play the game much anymore to spend time looking into it.

on elite BG CPU usage increases to 15-20% and game turns into a slideshow
i could not find any specific module that causes the problem, i think every one adds up
but even if i turn off main 'Enabled' toggle IceHUD remains number one in CPU usage
i played like that for years, so let it be :)
thanks anyway

I can't even imagine why it would still be using CPU when disabled...I will try to take a look, but that's super weird.