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SubjectRe: [PATCH] perf: Add a new sort order: SORT_INCLUSIVE (v4)
On 3/19/12 8:57 AM, Frederic Weisbecker wrote:

>>> Each hist have a period of 1, but the total period is 1.
>>> So the end result should be (IIUC):
>>>
>>> 100% foo a
>>> 100% foo b
>>> |
>>> --- a
>>> 100% foo c
>>> |
>>> --- b
>>> |
>>> --- c
>>>
>>
>> That is correct. The first column no longer adds up to 100%.
>
> So do we really want this?
>

I think so. It's a different way of presenting the data. Pie chart vs a
bar chart of OS market share where people may be using more than one OS.

I'll post some documentation updates.

>> If we don't do this, total_period will be inflated.
>
> Yeah right I've just tried and callchains look right. I'm just puzzled
> by the percentages:
>

Thanks for testing this!

> + 98,99% [k] execve
> + 98,99% [k] stub_execve
> + 98,99% [k] do_execve
> + 98,99% [k] do_execve_common
> + 98,99% [k] sys_execve
> + 53,12% [k] __libc_start_main
> + 53,12% [k] cmd_record

These look like they belong to the perf binary and are incorrectly
classified as kernel samples. Problem is that callchain_get() is not
populating the privilege level - it's simply propagating the privilege
level of the sample:


+ for (i = 0; i < cursor->nr; i++) {
+ struct addr_location al_child = *al;
+
+ err = callchain_get(&iter, &al_child);

Not all fields of al_child are populated by callchain_get().

> + 53,12% [k] T.101
> + 53,12% [k] main
> + 53,12% [k] run_builtin
> + 52,11% [k] perf_evlist__prepare_workload
> + 52,09% [k] T.1163

The rest of them look ok to me. If something doesn't make sense, please
point me at the output of "perf script".

>
>>
>>> Also this feature reminds me a lot the -b option in perf report.
>>> Branch sorting and callchain inclusive sorting are a bit different in
>>> the way they handle the things but the core idea is the same. Callchains
>>> are branches as well.
>>>
>>
>> Yes - I kept asking why the branch stack stuff doesn't use the
>> existing callchain logic.
>
> Because I fear that loops branches could make the tree representation useless.
>

The loops could happen in callgraphs too right (eg: recursive programs)?
The other problem in branch stacks/LBR is that they're sampled branches.
Just because I got a sample with:

a -> b
b -> c

doesn't necessarily mean that the callchain was a -> b -> c.

I still don't have the branch stack setup working properly. But I'm now
more sympathetic to the view that last branch sampling and callchains
may have different representations in perf.

-Arun


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