Macbook Pro (Late 2010) slow after installing Mavericks I've recently updated my 15-inch, Mid 2010 Macbook Pro to Mavericks. Since then, it's been running incredibly slow and tends to hang while using programs such as FireFox or Excel.

If I look at the activity monitor, the only task taking up a large amount of resources is kernal_task.

I've verified the hard drive through disk utility, and it said that the drive is fine. Here's the hardware overview, if that helps:


  Hardware Overview:
  
  Model Name: MacBook Pro
  
  Model Identifier:   MacBookPro6,2
  
  Processor Name: Intel Core i5
  
  Processor Speed:    2.53 GHz
  
  Number of Processors:   1
  
  Total Number of Cores:  2
  
  L2 Cache (per Core):    256 KB
  
  L3 Cache:   3 MB
  
  Memory: 4 GB
  
  Processor Interconnect Speed:   4.8 GT/s
  
  Boot ROM Version:   MBP61.0057.B0C


Does anyone know what could be causing this?
As Mathias711 pointed out in the comments, the cause of this was Spotlight automatically re-indexing after the after the OS upgrade. The process of indexing was greatly slowed down by OSX attempting to index a very slow, old external drive we had hooked up.

Once the indexing had finished (it actually took quite a while) the laptop eventually returned to its former speed. 

There's also a post by Computer World that backs up this conclusion:


  OS X will rebuild the Spotlight index after a major System upgrade. The process takes time and degrades performance while it takes place.
  
  Click on the Spotlight (looking glass) icon to the top right of the display to see if indexing is taking place. If indexing is in progress you should see a dot in the middle of the looking glass icon and/or be told the operation is taking place. Allow the process to complete and you should see immediate performance improvement.