Re: [PATCH v6 1/6] perf report: properly handle branch count in match_chain

[Andi Kleen]

On Thu, Oct 19, 2017 at 12:59:14PM +0200, Milian Wolff wrote:
> On Donnerstag, 19. Oktober 2017 00:41:04 CEST Andi Kleen wrote:
> > Milian Wolff <milian.wolff@xxxxxxxx> writes:
> > > +static enum match_result match_address_dso(struct dso *left_dso, u64
> > > left_ip, +					   struct dso *right_dso, u64 right_ip)
> > > +{
> > > +	if (left_dso == right_dso && left_ip == right_ip)
> > > +		return MATCH_EQ;
> > > +	else if (left_ip < right_ip)
> > > +		return MATCH_LT;
> > > +	else
> > > +		return MATCH_GT;
> > > +}
> > 
> > So why does only the first case check the dso? Does it not matter
> > for the others?
> > 
> > Either should be checked by none or by all.
> 
> I don't see why it should be checked. It is only required to prevent two 
> addresses to be considered equal while they are not. So only the one check is 
> required, otherwise we return either LT or GT.

When the comparison is always in the same process (which I think
is not the case) just checking the addresses is sufficient. If they are not then you
always need to check the DSO and only compare inside the same DSO.

-Andi