iMac activity monitor question

[anthony13]

Hi all,

So I have an iMac 2020 with the I9 and all the bells and whistles (details in my sig), but I've recently noticed when doing complex tasks or exports that tax the system and make the fan kick in, my activity monitor still only peaks out at about 20 total percent of the processor being used. it says 80 percent idle. The application in question meanwhile says it's using 100 percent of the CPU.

Is something amiss, is the application just not optimized, or am I reading the activity monitor wrong? (or all 3).

 

[wilberforce]

In activity monitor, for a particular process, 100% CPU means 100% of one logical core. If you have 10 cores = 20 logical cores using hyper-threading, then a process that uses all of the logical cores will report as using near 2000%. Some apps can only use one (real) core. An app that can't use more than one core is severely limited.

I have 8 cores (i7 2020 iMac), and here is an example, running Cinebench which uses all of my 16 logical cores, reporting near 1600%

I suggest display the "CPU History" window in activity monitor to see how many cores your app is actually using, like this (which is Lightroom importing and rendering previews):