sysprof 3.24 planning

[Christian Hergert <christian hergert me>]

Hi Everyone!

I just wanted to let people know about what I've been working on lately. 
Now that GNOME 3.22 is out the door I've been playing around with new 
ideas for Sysprof.

The basic gist is "visualizers".

As the sysprof capture format now supports generic counters, we can do 
some interesting things. We can start capturing cpu and memory usage, 
network traffic, GPU counters, Gtk/Clutter frame clock timing, etc etc

I've only implemented the CPU usage collector as part of the prototype, 
but it looks something like this:

https://people.gnome.org/~chergert/screenshots/sysprof/sysprof-visualizers.png

You can play with this on the wip/visualizers branch.

For this to get merged to master, I still need to implement selection 
support so that we can rebuild the callgraph based on the selected area. 
I think this will be particularly useful when diving into a particular 
hot spot.

Another important thing I'd like to fix this cycle is support for 
extracting symbols from the target machine. We currently do symbol 
resolution when building the callgraph (where as pre-3.20 we resolved at 
the end of the capture and then saved a XML file with resolved symbol 
names). This will allow us to have a hybrid approach where we can 
extract symbols when possible, but also point to a symbols directory in 
case the profiled machine has stripped binaries.

Something that is on my radar, but has had very little investigative 
work is remote profiling. I'd like to be able to SSH into a host and run 
the profiler remotely. This will help us in Builder as we start to 
support external hardware like tablets, phones, IoT, etc.

Cheers,

-- Christian