Re: [Valgrind-developers] Re: kcachegrind patch for valgrind-HEAD?

[Josef W. <Jos...@gm...>]

On Friday 04 October 2002 18:17, Jeremy Fitzhardinge wrote:
> On Fri, 2002-10-04 at 03:10, Josef Weidendorfer wrote:
> >    Suppose a call chain starting from A: A calls B and C; C calls A a=
gain.
>
> I don't think you should calculate anything at runtime; just record
> enough so you can do it all afterwards.  There shouldn't be a huge
> problem in working all this out: gprof does it, after all.

Perhaps I'm already logging to much with the "cumulative" costs of calls.
But I don't understand how to calculate this with self costs and call tre=
e=20
information alone, especially for functions taking part in multiple cycle=
s...


> Does this do what your example describes?
> ...

Yes :-)

> gprof generates this flat profile:
> ...

Seems quite correct :-)

> ...
> index % time    self  children    called     name
> [1]    100.0    0.03    0.23       1+2       <cycle 1 as a whole> [1]
>                 0.02    0.23       2             A <cycle 1> [3]

Why isn't "B <cycle1>" shown as child of <cycle1> ?

> ...
> [Handwave mode:] For the purposes of displaying a profile as a TreeMap,
> it seems to me that you need to break the graph up into strongly
> connected subgraphs, and display each of those as a node in your tree.

The subgraphs being the cycles with its children?

> When you want to descend into that node (ie display its sub-parts), you
> remove all the backwards edges (recursive calls) and treat it as a plai=
n
> tree.  When you remove the backwards edge, you can recompute the cost o=
f
> the subgraph without the recursion; the difference between the original
> cost and the new cost is how much you should attribute to the function
> which is making the recursive call.

I think I'm doing exactly this: Stop drawing at recursions...
And the problem is: I don't know what the cost of the recursive function=20
should be. I don't have the gprof results, but only my own logging.
I think I will have to dive into gprof algorithms a little bit...
As I understand at the moment, gprof never talks about recursive calls, b=
ut
makes "cycles" with subobjects.

Thanks anyway!

Josef