Re: [PATCH 2/5] perf script: extend db-export api to include callchains for samples

From: Chris Phlipot
Date: Sat Apr 23 2016 - 00:42:17 EST

On 04/22/2016 12:56 AM, Adrian Hunter wrote:
The call_paths table already has symbol_id which belongs uniquely to a DSO,
so why do we need dso_id as well?
If the symbol_id is 0 because the IP could not be resolved to a symbol, this is not necessarily a valid assumption. Without a dso_id in the call_paths table, it is not possible to resolve the dso when symbol information is missing. the db_export api currently does not have enough information to match a DSO with an IP.

It is often useful to still have the call path associated with a DSO even if there is no symbol, which i why i recommend keeping the dso_id in the call_paths table.
Why do you need a callback? Seems like the only thing you need from
thread-stack.c is the call path tree. You could move that to its own .c/.h
files and then process the call chain in db-export.c
My original intent was to reuse existing code with minimal changes and conform the existing design patterns they used. Thread-stack.c, for example, currently uses a callback to populate the call_return table, so I used a callback as well to populate the call_path table.

I am open to making this change if it is believed it will result in a cleaner implementation.

Also a list of changes like the one above heavily implies you are not
obeying the one patch == one change rule. Please try to make patches that
only do one thing and also run checkpatch.
While i can split this into a few smaller patches there is only really justification for applying all of them all together. If this is still preferred i can resubmit this in smaller parts.

If you don't mind, I'll let you respond to my comments before I comment on
any other patches.

Let me know if you have any additional comments.