The crazy thing I did to fix Yosemite performance

William H. Magill magill at
Sun Nov 2 11:43:48 PST 2014

> On Nov 2, 2014, at 1:57 PM, René J.V. Bertin <rjvbertin at> wrote:
> On Sunday November 02 2014 12:06:35 Jeff Singleton wrote:
>> Back story: In an attempt to figure out why the services mds and 
>> mdworker were running away with my CPU. Nothing I did resolved this, 
>> including putting every single folder except /Applications in the 
>> exception list for Spotlight. This is where I started editing 
> Did that include switching off indexing for the whole (boot) disk (mdutil -i off) followed by a reboot? That ought to have wiped your spotlight folder, presuming that the most likely performance culprit would be updating an existing (huge) database file ...

This problem (runaway MDs/MDWorker jobs) was also true in Mavericks.

I don't know how Apple "updates" the Spotlight database, but it is pretty clear that following a major upgrade, that database needs to be purged of all the old records which are basically duplicated by the new. Using Apple's methodology, this update apparently takes days.

Virtually all of the fixes involved "trashing" that Spotlight database in some fashion. A disk-wipe and re-install, is clearly one, which also has the benefit of trashing all of the various Cache databases created by various apps, as User/Library/Caches is not backed-up.

William H. Magill
# iMac11,3 Core i7 [2.93GHz - 8 GB 1067MHz] OS X 10.10
# Macmini6,1 Intel Core i5 [2.5 Ghz - 4GB 1600MHz] OS X 10.10 OSX Server (now dead)

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