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sysprof/TODO
Soren Sandmann df07f71539 Make this function return a list of immediate callers again. 
2006-10-09  Soren Sandmann <sandmann@daimi.au.dk>

	* profile.c (profile_list_callers): Make this function return a
	list of immediate callers again.

	* sysprof.c (build_gui): Change label back to "Callers"

	* process.c (get_kernel_symbols): Only attempt to read the kernel
	symbols once.
2006-10-11 05:37:24 +00:00

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Before 1.0.4:
* See if we can reproduce the problem where libraries didn't get correctly
reloaded after new versions were installed.
This is just the (deleted) problem.Turns out that the kernel
doesn't print (deleted) in all cases. Some possibilities:
- check that the inodes of the mapped file and the disk file
are the same (done in HEAD).
- check that the file was not modified after being mapped?
(Can we get the time it was mapped or opened?)
* Build system
- Create RPM package? See fedora-packaging-list for information
about how to package kernel modules. Lots of threads in
June 2005 and forward.
See also http://www.fedoraproject.org/wiki/Extras/KernelModuleProposal
Someone already did create a package - should be googlable.
* See if we can reproduce this: Press start without kernel module loaded,
then load kernel module and press start again. Segmentation fault.
* Test on x86-64.
* Consider renaming sysprof-module.[ch] to sysprof.[ch] to move it closer to
kernel naming conventions.
* Get rid of include of "../config.h" as that won't work in the latest
kernel. done in HEAD, need to check what if anything breaks with older
kernels.
Before 1.2:
* Make sure that labels look decent in case of "No Map" etc.
* Elf bugs:
- error handling for bin_parser is necessary.
* Find out why all apps have an "In file /usr/bin/<app binary>" below
_libc_main. If possible, maybe make up a name for it.
* vdso stuff:
- the "[vdso]" string should be #defined somewhere
- Does get_vdso_bytes() belong in process.c?
- Is basing on "[vdso]" always correct?
* Convert things like [heap] and [stack] to more understandable labels.
* Strategies for taking reliable stacktraces.
Three different kinds of files
- kernel
- vdso
- regular elf files
- kernel
- eh_frame annotations, in kernel or in kernel debug
- /proc/kallsyms
- userspace can look at _stext and _etext to determine
start and end of kernel text segment
- copying kernel stack to userspace
- it's always 4096 bytes these days
- heuristically determine functions based on address
- is eh_frame usually loaded into memory during normal
operation
- vdso
- assume its the same across processes, just look at
sysprof's own copy.
Done: vdso is done now
- send copy of it to userspace once, or for every
sample.
- regular elf
- usually have eh_frame section which is mapped into memory
during normal operation
- do stackwalk in kernel based on eh_frame
- eh_frame section is usually mapped into memory, so
no file reading in kernel would be necessary.
- do stackwalk in userland based on eh_frame
- do ebp based stackwalk in kernel
- do ebp based stackwalk in userland
- do heuristic stackwalk in kernel
- do heuristic stackwalk in userland
* "Expand all" is horrendously slow because update screenshot gets called
for every "expanded" signal.
* See if we can make "In file <blah>" not be treated as a recursive function.
Maybe simply treat each individual address in the file as a function.
Or try to parse the machine code. Positions that are called are likely
to be functions.
* Give more sensible 'error messages'. Ie., if you get permission denied for
a file, put "Permission denied" instead of "No map"
* crc32 checking probably doesn't belong in elfparser.c
* Rethink binparser. Maybe the default mode should be:
- there is a current offset
- you can move the cursor
- _goto()
- _align()
- you can read structs with "begin_struct (format) / end_struct()"
Or maybe just "set_format()" that would accept NULL?
- when you are reading a struct, you can skip records with _index()
- you can read fields with get_string/get_uint by passing a name.
- you can read anonymous strings and uints by passing NULL for name
This is allowed even when not reading structs. Or maybe this
should be separate functions. Advantages:
- they can skip ahead, unlike fields accessors
- you can access specific types (8,16,32,64)
- there is no "name" field
Disadvantage:
- the field accesors would need renaming.
bin_parser_get_uint_field ()
is not really that bad though.
Maybe begin_record() could return a structure you could
use to access that particular record? Would nicely solve
the problems with "goto" and "index".
bin_record_get_uint();
What should begin/end be called? They will have different
objects passed.
bin_parser_get_record (parser) -> record
bin_record_free (record);
- Maybe support for indirect strings? Ie., get_string() in elfparser
- This will require endianness to be a per-parser property. Which is
probably just fine. Although d-bus actually has
per-message endianness. Maybe there could be a settable
"endianness" property.
Also need to add error checking.
* Rename stack_stash_foreach_by_address() to stack_stash_foreach_unique(),
or maybe not ...
* Make it compilable against a non-running kernel.
* commandline version should check that the output file is writable
before starting the profiling.
* Maybe report idle time? Although this would come for free with the
timelines.
* Fix (deleted) problem. But more generally, whenever we can't display a
symbol, display an error message instead, ie.,
- 'Binary file <xxxx> was deleted/replaced'
- 'No mapping for address'
- 'No symbols in binary file'
- 'Address has no corrresponding symbol in file'
- etc.
done: HEAD will not load files with the wrong inode now.
* Consider deleting cmdline hack in process.c and replace with something at
the symbol resolution level. Will require more memory though.
* Add spew infrastructure to make remote debugging easier.
* Make it compile and work on x86-64
* With kernel module not installed, select Profiler->Start, then dismiss
the alert. This causes the start button to appear prelighted. Probably
just another gtk+ bug.
* Find out if the first sort order of a GtkTreeView column can be changed
programmatically.
- Fix bugs/performance issues:
- decorate_node should be done lazily
- Find out why we sometimes get completely ridicoulous stacktraces,
where main seems to be called from within Xlib etc. This happens
even after restarting everything.
- It looks like the stackstash-reorg code confuses "main" from
unrelated processes. - currently it looks like if multiple
"main"s are present, only one gets listed in the object list.
Seems to mostly happen when multiple processes are
involved.
- Numbers in caller view are completely screwed up.
- It looks like it sometimes gets confused with similar but different
processes: Something like:
process a spends 80% in foo() called from bar()
process b spends 1% in foo() called from baz()
we get reports of baz() using > 80% of the time.
Or something.
- add_trace_to_tree() might be a little slow when dealing with deeply
recursive profiles. Hypothesis: seen_nodes can grow large, and the
algorithm is O(n^2) in the length of the trace.
- make the things we put in a stackstash real
objects so that
- we can save them
- they will know how to delete the presentation
names and themselves (through a virtual function)
- they can contain markup etc.
- The unique_dup() scheme is somewhat confusing.
- a more pragmatic approach might be to just walk the tree and
save it.
- plug all the leaks
- loading and saving probably leak right now
- rethink loading and saving. Goals
- Can load 1.0 profiles
- Don't export too much of stackstashes to the rest of the
app
Features:
* Have a compatibility module that can load 1.0 modules
- reads in the call tree, then generate a stack stash
by repeatedly adding traces.
* Make stackstash able to save themselves using callbacks.
* If loading a file fails, then try loading it using the
1.0 loader.
- optimization: make sure we fail immediately if we
see an unknown object.
* Add versioning support to sfile.[ch]:
- sformat_new() should take doctype and version strings:
like "sysprof-profile" "version 1.2"
- there should be sfile_sniff() functionality that will
return the doctype and version of a file. Or None
if there aren't any.
* At this point, make the loader first check if the file has a version
if it doesn't, load as 1.0, otherwise as whatever the version claims
it is.
* Make provisions for forward compatibility: maybe it should be
possible to load records with more fields than specified.
* Figure out how to make sfile.[ch] use less memory.
- In general clean sfile.[ch] up a little:
- split out dfa in its own generic class
- make a generic representation of xml files with quarks for strings:
struct item {
int begin/end/text;
quark text: -> begin/end/value
int id; -> for begins that are pointed to
}
perhaps even with iterators. Should be compact and suitable for both
input and output. As a first cut, perhaps just split out the
Instruction code.
(done, somewhat).
- make the api saner; add format/content structs
Idea: all types have to be declared:
SFormat *format = sformat_new()
SType *object_list = stype_new (format);
SType *object = stype_new (format);
...
stype_define_list (object_list, "objects", object);
stype_define_record (object, "object",
name, total, self, NULL);
stype_define_pointer (...);
* See if the auto-expanding can be made more intelligent
- "Everything" should be expanded exactly one level
- all trees should be expanded at least one level
* Send entire stack to user space, then do stackwalking there. That would
allow us to do more complex algorithms, like dwarf, in userspace. Though
we'd lose the ability to do non-racy file naming. We could pass a list
of the process mappings with each stack though. Doing this would also solve
the problem of not being able to get maps of processes running as root.
Might be too expensive though. User stacks seem to be on the order
of 100K usually, which for 200 times a second means a bandwidth of
20MB/s, which is probably too much. One question is how much of it
usually changes.
Actually it seems that the _interesting_ part of the stack
(ie., from the stack pointer and up) is not that big in many cases. The
average stacksize seemed to be about 7700 bytes for gcc compiling gtk+.
Even deeply recursive apps like sysprof only generate about 55K stacks.
Other possibilities:
- Do heuristic stack walking where it lists all words on the stack
that look like they might be return addresses.
- Somehow map the application's stack pages into the client. This
is likely difficult or impossible.
- Another idea: copy all addresses that look like they could be
return addresses, along with the location on the stack. This
just might be enough for a userspace stack walker.
- Yet another: krh suggests hashing blocks of the stack, then
only sending the blocks that changed since last time.
- every time you send a stackblock, also send a cookie.
- whenever you *don't* send a stackblock, send the cookie
instead. That way you always get a complete stacktrace
conceptually.
- also, that would allow the kernel to just have a simple
hashtable containing the known blocks. Though, that could
become large. Actually there is no reason to store the
blocks; you can just send the hashcode. That way you
would only need to store a list of hashcodes that we
have generated previously.
* If interrupt happens in kernel mode, send both
kernel stack and user space stack, have userspace stitch them
together. well, they could be stitched together in the kernel.
Already done: we now take a stacktrace of the user space process
when the interrupt happens in kernel mode. (Unfortunately, this
causes lockups on many kernels (though I haven't seen that for
a while)).
We don't take any stacktraces of the kernel though. Things that
need to be
investigated:
- does the kernel come with dwarf debug information?
- does the kernel come with some other debug info
- is there a place where the vmlinux binary is usually
placed? (We should avoid any "location of vmlinux" type
questions if at all possible).
regarding crossing system call barriers: Find out about the virtual dso
that linux uses to do fast system calls:
http://lkml.org/lkml/2002/12/18/218
and what that actually makes the stack look like. (We may want to just
special case this fake dso in the symbol lookup code).
Maybe get_user_pages() is the way forward at least for some stuff.
note btw. that the kernel pages are only one or two pages, so we
could easily just dump them to userspace.
- See if there is a way to make it distcheck
- grep "FIXME - not10"
- translation should be hooked up
- Consider adding "at least 5% inclusive cost" filter
- consider having the ability to group a function together with its nearest
neighbours. That way we can eliminate some of the effect of
"one function taking 10% of the time"
vs.
"the same function broken into ten functions each taking 1%"
Not clear what the UI looks like though.
- Ability to generate "screenshots" suitable for mail/blog/etc
UI: "generate screenshot" menu item pops up a window with
a text area + a radio buttons "text/html". When you flick
them, the text area is automatically updated.
- beginning in CVS:
- why does the window not remember its position when
you close it with the close button, but does remember
it when you use the wm button or the menu item? It actually
seems that it only forgets the position when you click the
button with the mouse. But not if you use the keyboard ...
This is a gtk+ bug.
- Find out how gdb does backtraces; they may have a better way. Also
find out what dwarf2 is and how to use it. Look into libunwind.
It seems gdb is capable of doing backtraces of code that neither has
a framepointer nor has debug info. It appears gdb uses the contents
of the ".eh_frame" section. There is also an ".eh_frame_hdr" section.
http://www.linuxbase.org/spec/booksets/LSB-Embedded/LSB-Embedded/ehframe.html
look in dwarf2-frame.[ch] in the gdb distribution.
Also look at bozo-profiler
http://www-sop.inria.fr/dream/personnel/Mathieu.Lacage/bozo-profiler/bozo-profiler-1.1.tar.gz
which has an elf32 parser/debugger
- 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 what we do now: set the busy cursor unconditionally
- Consider adding 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
- probably need a dependency on gtk+ 2.8 (cairo) for this.
- Matthias has code for something like this.
- See http://www.marzocca.net/linux/baobab.html
- Also see http://www.cs.umd.edu/hcil/treemap-history/index.shtml
- Add support for line numbers within functions
- Possibly a special "view details" mode, assuming that
the details of a function are not that interesting
together with a tree. (Could add radio buttons somewhere in
in the right pane).
- Add view->ancestors/descendants menu items
- rethink caller list, not terribly useful at the moment. Federico suggested
listing all ancestors.
Done: implemented this idea in CVS HEAD. If we keep it that way,
should do a globale s/callers/ancestors on the code.
- not sure it's an improvement. Often it is more interesting to
find the immediate callers.
- Now it's back to just listing the immediate callers.
- Have kernel module report the file the address was found in
Should avoid a lot of potential broken/raciness with dlopen etc.
Probably better to send a list of maps with each trace.
- Figure out how Google's pprof script works. Then add real call graph
drawing. (google's script is really simple; uses dot from graphviz).
KCacheGrind also uses dot to do graph drawing.
- hide internal stuff in ProfileDescendant
- possibly add dependency on glib 2.8 if it is released at that point.
(g_file_replace())
* Some notes about timer interrupt handling in Linux
On an SMP system APIC is used - the interesting file is arch/i386/kernel/apic.c
On UP systems, the normal IRQ0 is used
When the interrupt happens,
entry.S
calls do_IRQ, which sets up the special interrupt stack,
and calls __do_IRQ, which is in /kernel/irq/handle.c.
This calls the corresponding irqaction, which has previously
been setup by arch/i386/mach-default/setup.c to point to
timer_interrupt, which is in arch/i386/kernel/time.c.
This calls do_timer_interrupt_hooks() which is defined in
/include/asm-i386/mach-default/do_timer.h. This function
then calls profile_tick().
Note when the CPU switches from user mode to kernel mode, it
pushes SS/ESP on top of the kernel stack, but when it switches
from kernel mode to kernel mode, it does _not_ push SS/ESP.
It does in both cases push EIP though.
Later:
- somehow get access to VSEnterprise profiler and see how it works.
somehow get access to vtune and see how it works.
- On SMP systems interrupts happen unpredictably, including when another
one is running. Right now we are ignoring any interrupts that happen
when another one is running, but we should probably just save the data
in a per-cpu buffer.
- Find out if sysprof accurately reports time spent handling pagefaults.
There is evidence that it doesn't:
- a version of sysprof took 10 seconds to load a certain profile.
Profiling itself it appeared that most of the time was spent
in the GMarkup parser
- a newer version of sysprof with significantly more compact
Instructions structure took about 5 seconds, but the profile
looked about the same.
The difference between the two versions has to be in page faults/
memory speed, but the profiles looked similar.
Try and reproduce this in a more controlled experiment.
- See if it is possible to group the X server activity under the process that
generated it.
- .desktop file
[Is this worth it? You will often want to start it as root,
and you will need to insert the module from the comman line]
- Applications should be able to say "start profiling", "stop profiling"
so that you can limit the profiling to specific areas.
Idea:
Add a new kernel interface that applications uses to say
begin/end.
Then add a timeline where you can mark interesting regions,
for example those that applications have marked interesting.
- Find out how to hack around gtk+ bug causing multiple double clicks
to get eaten.
- 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.
Note thought that scripting languages will generally have a stack with
both script-binary-stack, script stack, and library stacks. We wouldn't
want scripts to need to parse dwarf. Also if we do that thing with
sending the entire stack to userspace, things will be further complicated.
- Consider this usecase:
Someone is considering replacing malloc()/free() with a freelist
for a certain data structure. All use of this data structure is
confined to one function, foo(). It is now interesting to know
how much time that particular function spends on malloc() and free()
combined.
Possible UI:
- Select foo(),
- find an instance of malloc()
- shift-click on it,
- all traces with malloc are removed
- a new item "..." appears immeidately below foo()
- malloc is added below "..."
- same for free
- at this point, the desired data can be read at comulative
for "..."
Actually, with this UI, you could potentially get rid of the
caller list: Just present the call tree under an <everything> root,
and use ... to single out the stuff you are interested in.
Maybe also get rid of 'callers' by having a new "show details"
dialog or something.
The complete solution here degenerates into "expressions":
"foo" and ("malloc" or "free")
Having that would also take care of the "multiple functions"
above. Noone would understand it, though.
- 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. Also figure out how to deal with more than one CPU/core.
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. Then 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 used 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).
- Perhaps show a timeline with CPU in one color and disk in one color. Allow people to
look at at subintervals of this timeline. Is it useful to look at both CPU and disk at
the same time? Probably not. See also marker discussion above. UI should probably allow
double clicking on a marked section and all instances of that one would be marked.
- Other variation on the timeline idea: Instead of a disk timeline you could have a
list of individual diskaccesses, and be able to select the ones you wanted to
get rid of.
- The existing sysprof visualization is not terribly bad, the "self" column is
more useful now.
- See what files are accessed so that you can get a getter idea of what
the system is doing.
- Optimization usecases:
- A lot of stuff is read synchronously, but it is possible to read it asynchronously.
Visualization: A timeline with alternating CPU/disk activity.
- What function is doing all the synchronous reading, and what files/offsets is
it reading. Visualization: lots of reads across different files out of one
function
- A piece of the program is doing disk I/O. We can drop that entire piece of
code. Sysprof visualization is ok, although seeing the files accessed is useful
so that we can tell if those files are not just going to be used in
other places. (Gnumeric plugin_init()).
- A function is reading a file synchronously, but there is other (CPU/disk) stuff
that could be done at the same time. Visualization: A piece of the timeline
is diskbound with little or no CPU used.
- Want to improve code locality of library or binary. Visualization: no GUI, just
produce a list of functions that should be put first in the file. Then run the
program again until the list converges. (Valgrind may be more useful here).
- Nautilus reads a ton of files, icons + all the files in the homedirectory.
Normal sysprof visualization is probably useful enough.
- Profiling a login session.
- Many applications are running at the same time, doing IPC. It would be useful
if we could figure out what other things a given process is waiting on. Eg., in
poll, find out what processes have the other ends of the fd's open.
Visualization: multiple lines on a graph. Lines join up where one process
is blocking on another. That would show processes holding up the progress
very clearly.
This was suggested by Federico.
- Need to report stat() as well. (Where do inode data end up? In the buffer-cache?)
Also open() may cause disk reads (seeks).
- To generate the timeline we need to know when a disk request is issued and when it
is completed. This way we can assign blame to all applications that have issued a
disk request at a given point in time.
The disk timeline should probably vary in intensity with the number of outstanding
disk requests.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ALREADY DONE -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
* don't loop infinitely if there are cycles in the debuglink graph.
* Add "sysprof --version"
* Fix (potential) performance issues in symbol lookup.
- when an elf file is read, it should be checked that the various
sections are of the right type. For example the debug information
for emacs is just a stub file where all the sections are NOBITS.
* Try reproducing crash when profiling xrender demo
- it looks like it crashes when it attempts to read /usr/bin/python
- apparently what's going on is that one of the symbols in python's
dynamic symbol table has a completely crazy 'st_name' offset.
DONE: we didn't actually need to read the name at all,
but still should find out why that value is so weird.
It looks like there is something strange going on with that file.
All the dynsyms have weird info/type values, yet nm and readelf
have no problems displaying it.
- Can .gnu_debuglink recurse?
yes, it can, and we should probably not crash if there are
cycles in the graph.
* Find out why we are getting bogus symbols reported for /usr/bin/Xorg
Like this:
Everything 0.00 100.00
[/usr/bin/Xorg] 0.00 94.79
GetScratchPixmapHeader 0.00 94.79
__libc_start_main 0.00 94.79
FindAllClientResources 0.00 94.79
FreeFontPath 0.00 94.79
SProcRenderCreateConicalGradient 0.00 94.56
ProcRenderTrapezoids 0.00 94.56
AllocatePicture 0.00 94.56
__glXDispatch 0.00 0.16
__glXVendorPrivate 0.00 0.08
__glXRender 0.00 0.08
SmartScheduleStartTimer 0.00 0.08
[./sysprof] 0.00 2.76
[sshd: ssp@pts/0] 0.00 2.37
[compiz] 0.00 0.08
What's going on here is that the computed load address for the X server
binary is different for the debug binary. The lowest allocated address
is 0x08047134 for the normal, and 0x8048134 for the debug. But it looks
like the addresses are still the same for the symbols.
The root of this problem may be that we should ignore the load
address of the debug binary, and just lookup the address computed.
The *text* segments have the same address though. Everything from
"gnu version" on has the same address.
So:
- find out where in memory the text segment is
- take an address and compute its offset to the text segment
- in elf parser, find address of text segment
- add offset
- lookup resulting address
So basically, "load address" should really be text address. Except of course
that load_address is not used in process.c - instead the 'load address' of the
first part of the file is computed and assumed to be equivalent to the
load address. So to lookup something you probably actually need
to know the load/offset at the elf parser level:
lookup_symbol (elf, map, offset, address)
then,
real load address of text (lta) = map - offset + text_offset
offset of called func (ocf): addr - lta
thing to lookup in table: ocf + text_addr.loadaddr in debug
addr - map - offset + text_offset
hmmm ...
* plug all the leaks
- don't leak the presentation strings/objects
- maybe add stack_stash_set_free_func() or something
* Delete elf_parser_new() and rename elf_parser_new_from_file()
* Add demangling again
* Restore filename => binfile cache.
* It is apparently possible to get another timer interrupt in the middle
of timer_notify. If this happens the circular buffer gets screwed up and
you get crashes. Note this gets much worse on SMP (in fact how did this
work at all previously?)
Possible fixes
- have a "in timer notify" variable, then simply reject nested
interrupts
- keep a "ghost head" that timers can use to allocate new traces,
then update the real head whenever one of them completes. Note
though, that the traces will get generated in the wrong order
due to the nesting. In fact, only the outermost timernotify
can update the real head, and it should update it to ghost_head.
- do correct locking? Nah, that's crazy talk
Also note: a race is a race, and on SMP we probably can't even make it
unlikely enough to not matter.
Fixed by ignoring the nested interrupts using an atomic variable.
* When you load a file from the commandline, there is a weird flash of the toolbar.
What's going on is this:
- this file is loaded into a tree model
- the tree model is set for the function list
- this causes the selection changed signal to be emitted
- the callback for that signal process updates
- somehow in that update process, the toolbar flashes.
- turns out to be a gtk+ issue: 350517
- screenshot window must be cleared when you press start.
- Formats should become first-class, stand-alone objects that offers
help with parsing and nothing else.
ParseContext* format_get_parse_context (format, err);
gboolean parse_context_begin (parse_context, name, err);
gboolean parse_context_end (parse_format, name, err);
basically, a Format encapsulates a DFA, and a ParseContext encapsulates
the current state.
- make stackstash ref counted
- Charge 'self' properly to processes that don't get any stack trace at all
(probably we get that for free with stackstash reorganisation)
- CVS head now has two radio buttons in the right pane, and
caller pane is gone. (This turned out to be a bad idea, because it
is often useful to click on ancestors to move up the tree).
* Don't build the GUI if gtk+ is not installed
* Find out why we sometimes get reports of time spent by [pid 0].
* - Run a.out generated normally with gcc.
- Run sysprof
- hit profile
- Kill a.out
- strip a.out
- run a.out
- hit start
- hit profile
At this point we should not get any symbols, but we do. There is some
sort of bad caching going on.
* support more than one reader of the samples properly
- Don't generate them if noone cares
* Correctness
- When the module is unloaded, kill all processes blocking in read
- or block unloading until all processes have exited
Unfortunately this is basically impossible to do with a /proc
file (no open() notification). So, for 1.0 this will have to be
a dont-do-that-then. For 1.2, we should do it with a sysfs and
kobject instead.
- When the module is unloaded, can we somehow *guarantee* that no
kernel thread is active? Doesn't look like it; however we can
get close by decreasing a ref count just before returning
from the module. (There may still be return instructions etc.
that will get run). This may not be an issue with the timer
based scanning we are using currently.
* Find out why we get hangs with rawhide kernels. This only happens with the
'trace "current"' code. See this mail:
http://mail.nl.linux.org/kernelnewbies/2005-08/msg00157.html
esp0 points to top of kernel stack
esp points to top of user stack
(Reported by Kjartan Maraas).
- When not profiling, sysprof shouldn't keep the file open.
- 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
- should be easy to do with stackstash reorganization.
* Handle time being set back in the RESET_DEAD_PERIOD code.
- total should probably be cached so that compute_total() doesn't
take 80% of the time to generate a profile.
- Fixing the oops in kernels < 2.6.11
- Probably just require 2.6.11 (necessary for timer interrupt
based anyway).
- Make the process waiting in poll() responsible for extracting
the backtrace. Give a copy of the entire stack rather than doing
the walk inside the kernel.
New model:
- Two arrays,
one of actual scanned stacks
one of tasks that need to be scanned
One wait queue,
wait for data
- in read() wait for stack data:
scan_tasks()
if (!stack_data)
return -EWOULDBLOCK;
in poll()
while (!stack data) {
wait_for_data();
scan_tasks();
}
return READABLE;
scan_tasks() is a function that converts waiting
tasks into data, and wakes them up.
- in timer interrupt:
if (someone waiting in poll() &&
current && current != that_someone &&
current is runnable)
{
stop current;
add current to queue;
wake wait_for_data;
}
This way, we will have a real userspace process
that can take the page faults.
- Different approach:
pollable file where a regular userspace process
can read a pid. Any pid returned is guaranteed to be
UNINTERRUPTIBLE. Userspace process is required to
start it again when it is done with it.
Also provide interface to read arbitrary memory of
that process.
ptrace() could in principle do all this, but
unfortunately it sucks to continuously
ptrace() processes.
- Yet another
Userspace process can register itself as "profiler"
and pass in a filedescriptor where all sorts of
information is sent.
- could tie lifetime of module to profiler
- could send "module going away" information
- Can we map filedescriptors to files in
a module?
* Make sure sysprof-text is not linked to gtk+
* Consider renaming profiler.[ch] to collector.[ch]
* Crash reported by Rudi Chiarito with n_addrs == 0.
* Find out what distributions it actually works on
(ask for sucess/failure-stories in 1.0 releases)
* Add note in README about Ubuntu and Debian -dbg packages and how to get
debug symbols for X there.
stackstash reorg:
- make loading and saving work again.
- make stashes loadable and savable.
- add a way to convert 1.0 files to stashes
- Get rid of remaining uses of stack_stash_foreach(), then
rename stack_stash_foreach_reversed() to
stack_stash_foreach()
- stackstash should just take traces of addresses without knowing
anything about what those addresses mean.
- stacktraces should then begin with a process
- stackstash should be extended so that the "create_descendant"
and "create_ancestor" code in profile.c can use it directly.
At that point, get rid of the profile tree, and rename
profile.c to analyze.c.
- the profile tree will then just be a stackstash where the
addresses are presentation strings instead.
- Doing a profile will then amount to converting the raw stash
to one where the addresses have been looked up and converted to
presentation strings.
-=-=
- profile should take traces of pointers to presentation
objects without knowing anything about these presentation
objects.
- 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. Maybe just a map from stack nodes
to presentation objects.
- Make the Profile class use the stash directly instead of
building its own copy.
- store a stash in the profile class
- make sure descendants and callers can be
built from it.
- get rid of other stuff in the profile
struct
* Before 1.0:
- Update version numbers in source
- Make tarball
- Check that tarball works
- cvs commit
- cvs tag sysprof-1-0
- Update website
- Announce on Freshmeat
- Announce on gnome-announce
- Announce on kernel list.
- Announce on Gnomefiles
- Announce on news.gnome.org
- Send to slashdot/developers
- Announce on devtools list (?)
- Announce on Advogato
link to archive
* The handling of the global variable in signal-handler.[ch] needs to be
atomic - right now it isn't. The issue is what happens if a handled signal
arrives while we are manipulating the list?
* (User space stack must probably be done in a thread - kernel
stack must probably be taken in the interrupt itself?
- Why this difference? The page tables should still be loaded. Is it
because pages_present() doesn't work? No, turning it off doesn't help.
- It looks like this works. Get:
struct pt_regs *user_regs =
(void *)current->thread.esp0 - sizeof (struct pt_regs);
then use pages_present as usual to trace with user_regs; There could be
rare lockups though.
* 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.
Work done by Lorenzo:
http://www.colitti.com/lorenzo/software/gnome-startup/sysprof-text.diff
http://www.colitti.com/lorenzo/software/gnome-startup/sysprof.log
http://colitti.com/lorenzo/software/gnome-startup/
* consider caching [filename => bin_file]
* Check the kernel we are building against, if it is SMP or
less than 2.6.11, print a warning and suggest upgrading.
* Timer interrupt based
* Interface
- Consider expanding a few more levels of a new descendants tree
- Algorithm should be expand in proportion to the
"total" percentage. Basically consider 'total' the
likelyhood that the user is going to look at it.
- Maybe just; keep expanding the biggest total until
there is no more room or we run out of things to expand.
* Web page containing
- Screen shots
- Explanation of what it is
- Download
- Bug reporting
- Contact info
- Ask for sucess/failure reports
- hook up menu items view/start etc (or possibly get rid of them or
move them)
- Should do as suggested in the automake manual in the
chapter "when automake is not enough"
- add an "insert-module" target
- need to run depmod on install
- If the current profile has a name, display it in the title bar
- auto*?
- Find out if that PREFIX business in Makefile was really such
a great idea.
- 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.
- Is there a portable way of asking for the root password?
- Install a small suid program that only inserts the module?
(instant security hole ..)
- Need to make "make install" work (how do you know where to install
kernel modules?)
- in /lib/modules/`uname -r`/kernel/drivers/
- need to run depmod as root after that
- Then modprobe run as root should correctly find it.
- grep FIXME
- give profiles on the command line
- Hopefully the oops at the end of this file is gone now that
we use mmput/get_task_mm. For older kernels those symbols
are not exported though, so we will probably have to either
use the old way (directly accessing the mm's) or just not
support those kernels.
- 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
- Find out what happened here:
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: Unable to handle kernel NULL pointer dereference at virtual address 000001b8
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: printing eip:
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: c017342c
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: *pde = 00000000
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: Oops: 0000 [#1]
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: Modules linked in: sysprof_module(U) i2c_algo_bit md5 ipv6 parport_pc lp parport autofs4 sunrpc video button battery ac ohci1394 ieee1394 uhci_hcd ehci_hcd hw_random tpm_atmel tpm i2c_i801 i2c_core snd_intel8x0 snd_ac97_codec snd_pcm_oss snd_mixer_oss snd_pcm snd_timer snd soundcore snd_page_alloc e1000 floppy dm_snapshot dm_zero dm_mirror ext3 jbd dm_mod ata_piix libata sd_mod scsi_mod
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: CPU: 0
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: EIP: 0060:[<c017342c>] Not tainted VLI
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: EFLAGS: 00010287 (2.6.11-1.1225_FC4)
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: EIP is at grab_swap_token+0x35/0x21f
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: eax: 0bd48023 ebx: d831d028 ecx: 00000282 edx: 00000000
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: esi: c1b72934 edi: c1045820 ebp: c1b703f0 esp: c18dbdd8
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: ds: 007b es: 007b ss: 0068
Apr 11 15:42:08 great-sage-equal-to-heaven kernel: Process events/0 (pid: 3, threadinfo=c18db000 task=f7e62000)
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: Stack: 000011a8 00000000 000011a8 c1b703f0 c0151731 c016f58f 000011a8 c1b72934
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: 000011a8 c0166415 c1b72934 c1b72934 c0163768 ee7ccc38 f459fbf8 bf92e7b8
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: f6c6a934 c0103b92 bfdaba18 c1b703f0 00000001 c1b81bfc c1b72934 bfdaba18
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: Call Trace:
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0151731>] find_get_page+0x9/0x24
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c016f58f>] read_swap_cache_async+0x32/0x83Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0166415>] do_swap_page+0x262/0x600
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0163768>] pte_alloc_map+0xc6/0x1e6
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0103b92>] common_interrupt+0x1a/0x20
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c01673f0>] handle_mm_fault+0x1da/0x31d
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c016488e>] __follow_page+0xa2/0x10d
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0164a6f>] get_user_pages+0x145/0x6ee
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0161f66>] kmap_high+0x52/0x44e
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<c0103b92>] common_interrupt+0x1a/0x20
Apr 11 15:42:09 great-sage-equal-to-heaven kernel: [<f8cbb19d>] x_access_process_vm+0x111/0x1a5 [sysprof_module]
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<f8cbb24a>] read_user_space+0x19/0x1d [sysprof_module]
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<f8cbb293>] read_frame+0x35/0x51 [sysprof_module]
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<f8cbb33a>] generate_stack_trace+0x8b/0xb4
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<f8cbb3a2>] do_generate+0x3f/0xa0 [sysprof_module]
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c0138d7a>] worker_thread+0x1b0/0x450
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c0379ccd>] schedule+0x30d/0x780
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c011bdb6>] __wake_up_common+0x39/0x59
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<f8cbb363>] do_generate+0x0/0xa0 [sysprof_module]
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c011bd71>] default_wake_function+0x0/0xc
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c0138bca>] worker_thread+0x0/0x450
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c013f3cb>] kthread+0x87/0x8b
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c013f344>] kthread+0x0/0x8b
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: [<c0101275>] kernel_thread_helper+0x5/0xb
Apr 11 15:42:10 great-sage-equal-to-heaven kernel: Code: e0 8b 00 8b 50 74 8b 1d c4 55 3d c0 39
da 0f 84 9b 01 00 00 a1 60 fc 3c c0 39 05 30 ec 48 c0 78 05 83 c4 20 5b c3 a1 60 fc 3c c0 <3b> 82 b8 01 00 00 78 ee 81 3d ac 55 3d c0 3c 4b 24 1d 0f 85 78
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