On Mon, May 19, 2014 at 05:21:15PM +0900, Namhyung Kim wrote:
> This is gone with 540476de74c9 ("perf tools: Remove
> symbol_conf.use_callchain check").
The patchkit applies to tip/perf/core.
> > + * Check for overlap into the callchain.
> > + * The return address is one off compared to
> > + * the branch entry. To adjust for this
> > + * assume the calling instruction is not longer
> > + * than 8 bytes.
> > + */
> > + if (be[i].from < chain->ips[first_call] &&
> > + be[i].from >= chain->ips[first_call] - 8)
> > + first_call++;
>
> It seems that you need to check chain->ips[first_call] is greater than
> PERF_CONTEXT_MAX and use such value as the cpumode...
I don't understand the comment. The only IP that gets resolved is the from/to.
And add_callchain_ip does it own resolution.
Wouldn't make any sense to get it from first_call
>
>
> > + } else
> > + be[i] = branch->entries[branch->nr - i - 1];
> > + }
> > +
> > + nr = remove_loops(be, nr);
> > +
> > + for (i = 0; i < nr; i++) {
> > + err = add_callchain_ip(machine, thread, parent,
> > + root_al,
> > + -1, be[i].to);
> > + if (!err)
> > + err = add_callchain_ip(machine, thread,
> > + parent, root_al,
> > + -1, be[i].from);
>
> ... for here.
>
>
> > + if (err == -EINVAL)
> > + break;
> > + if (err)
> > + return err;
> > + }
> > + chain_nr -= nr;
>
> It seems it could make some callchain nodes being ignored. What if a
> case like small callchains with matches to only 2 nodes in the LBR?
>
> nr = 16, chain_nr = 10 and first_call = 2
The chain_nr variable is just to handle it when the user
specified a max_stack value. nr is always capped to max_stack too.
If lbr size is >= max_stack it will end up being 0 or negative and the
following loop to add normal call stack entries will do nothing.
I think that's the correct behavior.
-Andi
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