I have a 2010 MacBook Pro running OS X Yosemite with 4GB of RAM and 200+ GB of disk space. After switching users, the user who has just logged in is slow. Waiting several minutes or dropping to Terminal and running sudo killall -u $other_user -KILL seems to immediately show an improvement in performance.

The only consistent symptom I can find is that the other user has a number of processes, nearly all Chrome, using CPU cycles. I have not tracked this observation consistently enough to say if it is always true or not. When OS X switches users does it treat the other user as if the system were asleep or does it allow that users processes to run?

Killing another users running processes is poor manners. Is there a better way to solve this problem? What can I examine to determine why the system is slow after switching users?

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    See if you have some process using ssignificant memory in Activity Monitor? – FrontENG Nov 7 '16 at 4:18
  • @FrontENG see edits, it seems to be CPU more than Memory – Freiheit Nov 7 '16 at 14:45
  • What about disk activity? Also, try creating another user to test to see if it has to do with their profile. – Allan Nov 7 '16 at 14:48
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    @Allan - I have not captured metrics, but the disk is clearly grinding away after switching a user. I will make an effort to measure that. Good call on testing with another user! That would narrow it down as a general problem or a problem with one user in particular. – Freiheit Nov 7 '16 at 14:56
  • disk grinding here I would guess is swapping memory - and wen browseers take memory so look at the memory usage – mmmmmm Nov 7 '16 at 16:56

The problem was resolved by swapping in an SSD.

The root cause may still be memory swapping. I am not sure if I was truly I/O bound or if the SSD just swaps fast enough to not be a problem.

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