Profiling Vim

I like Vim because it’s very fast. Unfortunately the other day I found myself opening a diff file that took forever to load. The file had 58187 (this number will be important later on) lines in it but I never thought Vim would choke with something that was less than 2M size.

This post was originally published on medium

Finding out which plugin is making Vim slow

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If you find yourself in a similar situation this is what you can do in order to find out what is causing Vim to slow down.

1. Open Vim and start profiling

   :profile start /tmp/profile.log
   :profile func *
   :profile file *
   

   This is telling Vim to save the results of the profile into /tmp/profile.log and to run the profile for every file and function.

   Note: The profile.log file only gets generated until you close Vim.

2. Do the action that is taking a long time to run (in my case opening the diff file)

   :edit /tmp/file.diff
   :profile pause
   :q!
   

3. Analyze the data

   There is a lot of information in /tmp/profile.log but you can start by focusing on the Total time. In my case there was a clear offender with a total time of more than 14 seconds! And it looked like this:

   FUNCTION <SNR>24_PreviewColorInLine() 
   Called 58187 times 
   Total time: 14.430544 
   Self time: 2.961442
   

   Remember the number of lines in the file I mentioned before? For me it was interesting to see that the function gets called just as many times.

4. Pinpoint the offender

   Finding out where a function is defined is very easy thanks to the <SNR> tag and the number right after it. You simply need to run :scriptnames and scroll until you find the index number you are looking for, in my case 24.

   24: ~/.vim/bundle/colorizer/autoload/colorizer.vim
   

I opened up a GitHub issue to make the developers of the plugin aware but it seems as if the project has been left unmaintained so I decided to remove it from my vimrc file.