linux-kernel - Re: [PATCH v6 1/6] perf report: properly handle branch count in match

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Message-ID: <20171019150108.GA24104@danjae.aot.lge.com>
Date:   Fri, 20 Oct 2017 00:01:08 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Milian Wolff <milian.wolff@...b.com>, acme@...nel.org,
        jolsa@...nel.org, Linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Yao Jin <yao.jin@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        kernel-team@....com
Subject: Re: [PATCH v6 1/6] perf report: properly handle branch count in
 match_chain

Hi Andi,

On Thu, Oct 19, 2017 at 06:55:19AM -0700, Andi Kleen wrote:
> 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@...b.com> 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.

As far as I know, the node->ip is a relative address (inside a DSO).
So it should compare the dso as well even in the same process.

Thanks,
Namhyung