Emacs responds slow: how to profile?

Question

I'm sometimes experiencing some Emacs. Sometimes emacs spends an awful lot of time in saving a file. I haven't quite figured out why and when it happens. It seems to occur when using IPython and ropemacs.

Is there a way to find out one what emacs spends its time? Note that emacs does not respond during "saving" the file.

Another thread on profiling emacs did not provide a clear solution.

Can anybody recommend me what steps to undertake to find out what is keeping emacs busy. As said, it occurs when running the ipython shell and when I'm working with ropemacs to link myself a way through a lot of code. Or, does anybody know of issues with these packages? Or, Is is an operating system issue? (I have ubuntu 11.10, emacs 23.3.1, ipython 0.11)

Answer 1

Someone else will no doubt give you advice about profiling. What I would do, personally, is find out what function starts the save operation, and then use the Emacs debugger at the point where the save starts --- either add (debug) just before the overall save operation or use M-x debug-on-entry for the function that initiates the save.

I would step through the debugger (using d and c) to see what the time-consuming step is. If I had to guess blindly I'd guess that some application-level (e.g. python-related) massaging/transformation or validation of the data to be saved is occurring before the actual disk write.

Among other things, this will give you a better understanding of what's going on, and why.

Answer 2

For an overview of your profiling options, see this related question; you can use the tips in my answer there to profile specific packages that you suspect of causing the slow-downs.