Charge to callers

[bzbarsky]

I use this quite often in Instruments, especially in combination with the "collapse recursion" option (which I will file a separate issue about). That allows effectively collapsing A -> B -> A -> B recursion.

cc @gregtatum

[gregtatum]

Here's my assumption on how this will be implemented. Please correct me if I'm wrong in the details. The % is the self time.

                  Charge B to caller
                  |
                  v
Before: A (1%) -> B (2%) -> C (5%)
After: A (3%) -> C (5%)

Elsewhere in the call tree:

Before: D (4%) -> B (1%) -> E (5%) ...
After: D (5%) -> E (5%) ...

Would you like this reflected in the timeline flame chart as well?

[bzbarsky]

The percentages there look right, yes.

No opinion on the flame chart; I haven't used it enough to say much about it.

[julienw]

Should we implement this as a revertable filter (like "javascript only") or irreversible change (we lose information) ? My preference is the first (easier to reason about, easier to persist in the URL too), but this could have performance issues.

[bzbarsky]

This should absolutely be a revertable filter, because multiple versions of this for different functions might need to be tried, in various combinations, to make sense of the profile.

[gregtatum]

I filed bug #412 to address some of the issues with filtering, but I also think I found the bug that's blocking call tree filtering landing in the process. Hopefully I'll get a working patch soon.