linux-kernel - Re: [PATCH V6 6/8] perf/tools: Extend branch type classification

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Date:   Wed, 15 Jun 2022 14:39:01 +0100
From:   German Gomez <german.gomez@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        peterz@...radead.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, acme@...nel.org
Cc:     Robin Murphy <robin.murphy@....com>,
        Suzuki Poulose <suzuki.poulose@....com>,
        James Clark <james.clark@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V6 6/8] perf/tools: Extend branch type classification


On 15/06/2022 04:21, Anshuman Khandual wrote:
> [...]
>  
> +const char *get_branch_type(struct branch_entry *e)
> +{
> +	if (e->flags.type == PERF_BR_UNKNOWN)
> +		return "";
>> There is a small change of behavior in "perf script --field brstack".
>> Unknown branches were printed as "-" before but now it's an empty
>> string.
> get_branch_type() replaces print output in two different functions.
> branch_stack__printf() used to print a space " " for PERF_BR_UNKNOWN,
> and print_bstack_flags() used to print a "-" for PERF_BR_UNKNOWN.
> When they are factorized via get_branch_type(), one of those print
> formats need to be choosen.

Thanks for clarifying, Anshuman. I only bring it up in case somebody is
parsing this line for their use case. While running on x86 I came across
some UNKNOWN branches during my runs.

I have updated and sent a generic branch stack sampling perf test that
supports both ("-" and empty string) just in case. Hope it's useful.

https://lore.kernel.org/all/20220615130901.1151397-1-german.gomez@arm.com/

Thanks,
German