linux-kernel - Re: [PATCH v7 1/5] perf report: properly handle branch count in match

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Date:   Mon, 23 Oct 2017 13:39:39 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Milian Wolff <milian.wolff@...b.com>
Cc:     acme@...nel.org, jolsa@...nel.org, namhyung@...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>
Subject: Re: [PATCH v7 1/5] perf report: properly handle branch count in match_chain

Milian Wolff <milian.wolff@...b.com> writes:
>  		bi = sample__resolve_bstack(sample, al);
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 94d8f1ccedd9..e54741308e6c 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1824,6 +1824,8 @@ struct branch_info *sample__resolve_bstack(struct 
> perf_sample *sample,
>  		ip__resolve_ams(al->thread, &bi[i].to, bs->entries[i].to);
>  		ip__resolve_ams(al->thread, &bi[i].from, bs->entries[i].from);
>  		bi[i].flags = bs->entries[i].flags;
> +		if (bi[i].flags.cycles == 0)
> +			bi[i].flags.cycles = 123;
>  	}
>  	return bi;
>  }
>
> And then I ran again the two perf commands quoted above, but still cannot see 
> any avg_cycles. Am I missing something else? Or could you or someone else with 
> access to the proper hardware maybe test this?

The patch above was for annotate. For the call graphs you need to add
the fake cycles in the call graph path.

> I'd still be interested in seeing source code for an example binary as well as 
> the perf commands that should be used.

When supported, it works with any binary with -b
(see http://halobates.de/applicative-mental-models.pdf)

% cat tcall.c
volatile a = 10000, b = 100000, c;

__attribute__((noinline)) f2()
{
        c = a / b;
}

__attribute__((noinline)) f1()
{
        f2();
        f2();
}

main()
{
        int i;
        for (i = 0; i < 500000000; i++)
            f1();
}


% perf record -b  ./tcall

% perf report --branch-history --stdio
   78.68%  tcall.c:6              [.] f2                  tcall            
            |          
            |--39.56%--f1 tcall.c:12
            |          f2 tcall.c:7 (cycles:7)
            |          f2 tcall.c:6
            |          f1 tcall.c:12 (cycles:1)
            |          main tcall.c:17
            |          f2 tcall.c:7 (cycles:7)
            |          main tcall.c:18
            |          main tcall.c:17 (cycles:1)
            |          f1 tcall.c:11
            |          main tcall.c:18 (cycles:1)
            |          f2 tcall.c:6
            |          f1 tcall.c:11 (cycles:1)
            |          f1 tcall.c:12
            |          f2 tcall.c:7 (cycles:7)
            |          f2 tcall.c:6
            |          f1 tcall.c:12 (cycles:1)
            |          main tcall.c:17
            |          f2 tcall.c:7 (cycles:7)
            |          main tcall.c:18
            |          main tcall.c:17 (cycles:1)


-Andi