Messages in this thread | | | Date | Fri, 23 May 2014 14:35:03 -0700 | From | Andi Kleen <> | Subject | Re: [PATCH 1/9] perf, tools: Support handling complete branch stacks as histograms v6 |
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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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