3

I don't switch very often between the two accounts on my computer, so I'm thinking of just disabling fast user switching if it takes up significant system resources. Any idea if it takes up significant CPU, RAM, etc?

maxedison
  • 249

1 Answers1

4

It doesn't take up any extra resources to have it enabled; it will use extra resources if you use it. Specifically, if you fast-switch from one user account to another (instead of logging out and then back in as the other user), then all of the programs (both visible apps and background agents) running in the first user's login session continue to run and consume resources.

  • Programs left open in the session you switched away from are still loaded and still use RAM. How much depends entirely on what programs you had open and how memory-hungry they were.

  • Programs running in the session you switched away from may continue to use CPU, but usually not enough to matter. You're not interacting with them anymore, so (unless they're doing something like background data processing) they shouldn't be doing very much. Also, modern CPUs have several cores, and can run several processes at the same time, so even if something is running, it's probably running on a core you weren't using anyway.

    If you want to see how busy the CPU cores are, open the Activity Monitor utility, and choose Window menu > CPU Usage. I'll pop open a window showing how many cores you have (including virtual ones), and how busy each is. You can also use Activity Monitor's main window to examine all the running programs to see which are using lots of RAM, CPU, and other resources.

Gordon Davisson
  • 36,087