how to prevent numerous background daemons from harming gaming FPS (or other intense foreground workload performance)?

Question

One or another of the various macOS background daemons that comes with the operating system is always popping up and using a ton of CPU in the background. This is generally slightly bothersome, but it's really annoying while I'm trying to play demanding video games that really need the system's full attention. This visibly hurts the framerate and I need to go and investigate in iStat Menus or something to nuke the offending process manually.

Is there a way to comprehensively pause or at least aggressively throttle all system background activity while I'm doing something demanding? Mostly I want this for applications that are demanding of input responsiveness, like video games, but it would be nice for CPU intensive batch jobs that might take an hour or two to run, too; tell the system to please chill out in the background and not suck up either CPU or I/O to let the jobs run either more repsonsively or faster.

I'm being non-specific because “Why is daemon X taking up so much CPU” is a common genre of question on this site and others like it (previously, previously, previously, previously, previously, previously, previously, previously, previously, previously, previously). All of these daemons are implicated at various points. Probably the worst offenders are syspolicyd, AMPDevicesAgent, and worst of all suggestd, but all the usual suspects show up at one point or another.

As such, I'm not looking for a permanent answer for how to fix these problems all the time, i.e. how to make these daemons go away, because:

1. There's too many of them; I am resigned to just having weird energy leaks and performance problems until Apple provides some more transparency for their background daemons.
2. At least for right now, they're mostly behaving themselves most of the time, and I realize they provide value by indexing things and doing stuff in the background to provide responsiveness in the moment.
3. With an Apple Silicon machine, they appear to mostly be persistently scheduled onto the Efficiency cores and have less of a devastating performance and battery impact than they used to, as a result.

What I'm looking for is more of a temporary fix for when I need maximum performance, which would allow me to simply quiet down the background performance interference rather than shutting it down completely. I know the system needs this stuff to run for all the functionality to work and I don't want to take an axe to necessary parts of the OS, but I'd also like to get a consistent 120 FPS in 5-year-old games without dropping to 2-3FPS for a minute and getting killed because it was really important to Mail.app to make sure I could instantly search for some direct marketer's phone number because it downloaded a new message into its spam folder.

Answer 1

The answer to this is that it was a missing feature in macOS, and in macOS Sonoma now has Game Mode, which will have no configuration, but the OS should detect full-screen games and prioritize them.

Update 2024-08-26: In my experience, this feature doesn't work. In fact, it anti-works. It automatically activates in most games (Minecraft, Baldur's Gate 3, Borderlands 2, to name a few) and if I leave it on, it tanks my framerate and makes my input latency absolutely horrible. So the question remains open.

Answer 2

As nohillside suggested, using pkill -STOP suggestd works just fine. The process will be kept in the state "sleeping" once the command is executed (visible in the activity monitor, but using 0% CPU) (Note: I've checked the processes for more than five days and they were kept in "sleeping" mode.). If you want to prevent such processes from getting activated automatically, add the command into .bashrc (or other config). For example, in my case I have the following lines in .zshrc:

pkill -STOP suggestd
pkill -STOP photoanalysisd
pkill -STOP photolibraryd
pkill -STOP cloudphotod

Those processes will be running, but not using any CPU, because they will be "sleeping". You can verify the state yourself by finding the PID of the process and then looking at its state with top:

pgrep suggestd
# outputs <PID>
top -pid <PID>
# look for column `state`, it should be `sleeping`

Answer 3

You can pause long-running background processes like suggestd by running

pkill -STOP suggestd

To let it continue, use pkill -CONT suggestd (or reboot).

Answer 4

I wouldn't suggest killing these daemons as some of them are actually essential for the Mac to run. First install homebrew in terminal if you don't already have it. Then install top through homebrew. Locate the daemon that is hogging the cpu. You can validate if it is actually hogging the cpu by its corresponding % core usage. Click the nice + button. Nice is the prioritising order that you can play around with. 0 is default, as you increase the nice level, it loses priority to cpu space. 20 is the bottom of the pecking order. Whereas if you go downwards(negative) from 0, it increases the priority, and -20 is top priority. Htop allows you to increase the nice/decrease the priority, but not the other way without root permission.

So locate the daemon and crank its ice value up. If you don't want it to ever bother you again, max it up at 20. but it means if the cpu is running short on space, that daemon will never get around to running. So use this with care.