sysprof/TODO

Before 1.0:

* Correctness
	- grep FIXME
	- When the module is unloaded, kill all processes blocking in read

* Interface
	- If the current profile has a name, display it in the title bar
	- Sould just install the kernel module if it running as root, pop up
	  a dialog if not. Note we must be able to start without module now, 
	  since it is useful to just load profiles from disk.
        - hook up menu items view/start etc (or possibly get rid of them or
	  move them)
	- Consider expanding a few more levels of a new descendants tree 
	- give profiles on the command line

* Build system
	- Need to make "make install" work (how do you know where to install
	  kernel modules?)
	- Find out what distributions it actually works on
	    (ask for sucess/failure-stories in 0.9.x releases)
	- auto*?
	- .desktop file
	- translation should be hooked up 

Before 1.2:

- Make busy cursors more intelligent
	- when you click something in the main list and we don't respond
		within 50ms (or perhaps when we expect to not be able to do
		so (can we know the size in advance?))
	- instead of as we do now: set the busy cursor unconditionally
- Reorganise stackstash and profile

	- stackstash should just take traces of addresses without knowing
	  anything about what those addresses mean

	- stacktraces should then begin with a process

	- profile should take traces of pointers to presentation
	  objects without knowing anything about these presentation
	  objects.

	- Creating a profile is then

		- For each stack node, compute a presentation object
			(probably need to export opaque stacknode objects
			  with set/get_user_data)

		- Send each stack trace to the profile module, along with
		  presentation objects

- Charge 'self' properly to processes that don't get any stack trace at all 
	(probably we get that for free with stackstash reorganisation)

- support more than one reader of the samples properly
	- Don't generate them if noone cares
	- When not profiling, sysprof shouldn't care

- Add ability to show more than one function at a time. Algorithm:
	Find all relevant nodes;
	For each relevant node
		best_so_far = relevant node
		walk towards root
			if node is relevant,
				best_so_far = relevant
	        add best_so_far to interesting
	for each interesting
		list leaves
		for each leaf
			add trace to tree (leaf, interesting)
- Consider adding KDE-style nested callgraph view
- Add support for line numbers within functions
- consider caching [filename => bin_file]

- Have kernel module report the file the address was found in
	Should avoid a lot of potential broken/raciness with dlopen etc.
- Make things faster
	- Can I get it to profile itself?
	- speedprof seems to report that lots of time is spent in 
	  stack_stash_foreach() and also in generate_key()
- add an 'everything' object. It is really needed for a lot of things
- make profile.c more agnostic to processes and functions etc. Ideally
  it should just take a set of stack traces containing "presentation
  objects" and do something sensible with it.

- Non-GUI version that can save in a format the GUI can understand.
  Could be used for profiling startup etc. Would preferably be able to
  dump the data to a network socket. Should be able to react to eg.
  SIGUSR1 by dumping the data.

- Figure out how Google's pprof script works. Then add real call graph 
  drawing. (google's script is really simple; uses dot from graphviz).

- hide internal stuff in ProfileDescendant

Later:

- Find out how to hack around gtk+ bug causing multiple double clicks 
  to get eaten.

- Figure out what a 'disk profiler' is.

- Consider what it would take to take stacktraces of other languages

	- perl, 
	- python
	- java
	- bash

  Possible solution is for the script binaries to have a function
  called something like 

	__sysprof__generate_stacktrace (char **functions, int n_functions);

  that the sysprof kernel module could call (and make return to the kernel).

  This function would behave essentially like a signal handler: couldn't
  call malloc(), couldn't call printf(), etc. 
  
- figure out a way to deal with both disk and CPU. Need to make sure that
  things that are UNINTERRUPTIBLE while there are RUNNING tasks are not
  considered bad.

  Not entirely clear that the sysprof visualization is right for disk.

  Maybe assign a size of n to traces with n *unique* disk access (ie. 
  disk accesses that are not required by any other stack trace).

  Or assign values to nodes in the calltree based on how many diskaccesses
  are contained in that tree. Ie., if I get rid of this branch, how many
  disk accesses would that get rid of.

  Or turn it around and look at individual disk accesses and see what it
  would take to get rid of it. Ie., a number of traces are associated with
  any given diskaccess. Just show those. 

  Or for a given tree with contained disk accesses, figure out what *other*
  traces has the same diskaccesses.

  Or visualize a set of squares with a color that is more saturated depending
  on the number of unique stack traces that access it. The look for the
  lightly saturated ones. 

  The input to the profiler would basically be

	(stack trace, badness, cookie)

   For CPU:     badness=10ms,					      cookie=<a new one always>
   For Disk:    badness=<calculated based on previous disk accesses>, cookie=<the accessed disk block>

   For Memory:  badness=<cache line size not in cache>,		      cookie=<the address>

   Cookies are use to figure out whether an access is really the same, ie., for two identical
   cookies, the size is still just one, however 
   
   Memory is different from disk because you can't reasonably assume that stuff that has
   been read will stay in cache (for short profile runs you can assume that with disk,
   but not for long ones).

DONE:

- Need an icon

- hook up about box

- Add busy cursors,
	- when you hit "Profile"
	- when you click something in the main list and we don't respond
		within 50ms (or perhaps when we expect to not be able to do
		so (can we know the size in advance?))

- kernel module should put process to sleep before sampling. Should get us
  more accurate data

- Make sure samples label shows correct nunber after Open

- Move "samples" label to the toolbar, then get rid of statusbar.

- crashes when you ctrl-click the selected item in the top left pane
   <ian__> ssp: looks like it doesn't handle the none-selected case

- loading and saving

- consider making ProfileObject more of an object.

- make an "everything" object
       maybe not necessary -- there is a libc_ctors_something()

- make presentation strings nicer

  four different kinds of symbols:

       a) I know exactly what this is
       b) I know in what library this is
       c) I know only the process that did this
       d) I know the name, but there is another similarly named one

  (a) is easy,  (b) should be <in ...>    (c) should just become "???" 
  (d) not sure

- processes with a cmdline of "" should get a [pid = %d] instead.

- make an "n samples" label
Process stuff:

- make threads be reported together 
  (simply report pids with similar command lines together)
  (note: it seems separating by pid is way too slow (uses too much memory),
  so it has to be like this)

- stack stash should allow different pids to refer to the same root
  (ie. there is no need to create a new tree for each pid)
   The *leaves* should contain the pid, not the root. You could even imagine
   a set of processes, each referring to a set of leaves. 

- when we see a new pid, immediately capture its mappings

Road map:
     - new object Process
       - hashable by pointer
       - contains list of maps
       - process_from_pid (pid_t pid, gboolean join_threads)
       	 - new processes are gets their maps immediately
	 - resulting pointer must be unref()ed, but it is possible it
	   just points to an existing process
	 - processes with identical cmdlines are taken together
       - method lookup_symbol()
       - method get_name()
       - ref/unref
     - StackStash stores map from process to leaves
     - Profile is called with processes

It is possible that we simply need a better concept of Process:

     If two pids have the same command line, consider them the same, period.
     This should save considerable amounts of memory.

     The assumptions: 

     	 "No pids are reused during a profiling run"
	 "Two processes with the same command line have the same mappings"

     are somewhat dubious, but probably necessary.

     (More complex kernel:

     	   have the module report
	   	
		- new pid arrived (along with mappings)
		- mapping changed for pid
		- stacktrace)

- make symbols in executable work
- the hashtables used in profile.c should not accept NULL as the key
- make callers work
- autoexpand descendant tree
- make double clicks work
- fix leaks