Re: How to see where emacs memory goes to

[Stefan Monnier <monnier@iro.umontreal.ca>]

> My emacs currently consumes 256Mb virtual, and 125Mb resident.
> Its also fairly slow. This happens a lot with my usage pattern.

> Im trying to get a feel for where the memory consumption and slowness
> occur, and Im looking for techniques. Any hints would be apreciated.

> I currently look at these things:
> - m-x garbage-collect to get a baseline
> - how large the buffers are, including "hidden" ones
> - looking at the number of overlays in certain buffers.

> None of these factors seem to come even close to the numbers I get.

You can google for memory-usage.el which basially analyses the output of
garbage-collect and a few more things to give you some info, but it's
probably not going to help you much (it doesn't give you much more info
than garbage-collect, it's just more readable).

I think it would be helpful to try and come up with some better way to track
down such problems, but it's a difficult subject.  One way I can think of is
that in alloc.c we could change mark_object to keep a running count of
the amount of live-memory marked.  Then we could provide a command like
(memory-footprint &rest OBJECTS) which would return the amount of live
memory that would be dead if it weren't for OBJECTS.  It could be
implemented as follows:

   - set the mark bit on all OBJECTS
   - go through the complete normal mark phase
   - set live_memory_count back to 0 and clear the mark bit on OBJECTS
   - call mark_object on all OBJECTS
   - finish the GC by calling ther sweep phase
   - return live_memory_count.

> Currently it seems ERC is causing a lot of the slowness, if not the
> memory consumption.

Try to kill buffers one by one, and watch how the memory-usage change with
each kill.


        Stefan