linux-kernel - Re: [PATCH 2/4] perf: Print branch stack entry type in --dump-raw-trace

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Message-ID: <fb9717bb-735a-88d9-254d-0e7b2f7209f2@arm.com>
Date:   Tue, 8 Mar 2022 09:59:24 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     James Clark <james.clark@....com>, acme@...nel.org,
        linux-perf-users@...r.kernel.org
Cc:     german.gomez@....com, leo.yan@...aro.com,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] perf: Print branch stack entry type in
 --dump-raw-trace



On 3/7/22 22:49, James Clark wrote:
> This can help with debugging issues. It only prints when -j save_type
> is used otherwise an empty string is printed.

Specifying events with PERF_SAMPLE_BRANCH_CALL_STACK flag explicitly might
be better along with '-j save_type'.

> 
> Before the change:
> 
>   101603801707130 0xa70 [0x630]: PERF_RECORD_SAMPLE(IP, 0x2): 1108/1108: 0xffff9c1df24c period: 10694 addr: 0
>   ... branch stack: nr:64
>   .....  0: 0000ffff9c26029c -> 0000ffff9c26f340 0 cycles  P   0
>   .....  1: 0000ffff9c2601bc -> 0000ffff9c26f340 0 cycles  P   0
> 
> After the change:
> 
>   101603801707130 0xa70 [0x630]: PERF_RECORD_SAMPLE(IP, 0x2): 1108/1108: 0xffff9c1df24c period: 10694 addr: 0
>   ... branch stack: nr:64
>   .....  0: 0000ffff9c26029c -> 0000ffff9c26f340 0 cycles  P   0 CALL
>   .....  1: 0000ffff9c2601bc -> 0000ffff9c26f340 0 cycles  P   0 IND_CALL
> 
> Signed-off-by: James Clark <james.clark@....com>
> ---
>  tools/perf/util/session.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index f54282d5c648..3b8dfe603e50 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1159,14 +1159,15 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
>  		struct branch_entry *e = &entries[i];
>  
>  		if (!callstack) {
> -			printf("..... %2"PRIu64": %016" PRIx64 " -> %016" PRIx64 " %hu cycles %s%s%s%s %x\n",
> +			printf("..... %2"PRIu64": %016" PRIx64 " -> %016" PRIx64 " %hu cycles %s%s%s%s %x %s\n",
>  				i, e->from, e->to,
>  				(unsigned short)e->flags.cycles,
>  				e->flags.mispred ? "M" : " ",
>  				e->flags.predicted ? "P" : " ",
>  				e->flags.abort ? "A" : " ",
>  				e->flags.in_tx ? "T" : " ",
> -				(unsigned)e->flags.reserved);
> +				(unsigned)e->flags.reserved,
> +				e->flags.type ? branch_type_name(e->flags.type) : "");
>  		} else {
>  			printf("..... %2"PRIu64": %016" PRIx64 "\n",
>  				i, i > 0 ? e->from : e->to);

LGTM but I am wondering whether this might affect existing tools ?