linux-kernel - Re: [PATCH] perf: Fix missing raw data on tracepoint events

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Date:   Mon, 17 Oct 2022 23:38:09 +0000
From:   SeongJae Park <sj@...nel.org>
To:     James Clark <james.clark@....com>
Cc:     sj@...nel.org, linux-perf-users@...r.kernel.org,
        peterz@...radead.org, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH] perf: Fix missing raw data on tracepoint events

On Wed, 12 Oct 2022 15:38:57 +0100 James Clark <james.clark@....com> wrote:

> Since commit 838d9bb62d13 ("perf: Use sample_flags for raw_data")
> raw data is not being output on tracepoints due to the PERF_SAMPLE_RAW
> field not being set. Fix this by setting it for tracepoint events.

I was also getting similar issue[1], and confirmed that this fixes it.  Thank
you for the fix!  Also, thank you for pointing me to this patch, Namhyung!

> 
> This fixes the following test failure:
> 
>   perf test "sched_switch" -vvv
> 
>    35: Track with sched_switch
>   --- start ---
>   test child forked, pid 1828
>   ...
>   Using CPUID 0x00000000410fd400
>   sched_switch: cpu: 2 prev_tid -14687 next_tid 0
>   sched_switch: cpu: 2 prev_tid -14687 next_tid 0
>   Missing sched_switch events
>   4613 events recorded
>   test child finished with -1
>   ---- end ----
>   Track with sched_switch: FAILED!
> 
> Fixes: 838d9bb62d13 ("perf: Use sample_flags for raw_data")
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: James Clark <james.clark@....com>

Tested-by: SeongJae Park <sj@...nel.org>


[1] https://lore.kernel.org/bpf/20221017192744.1403-1-sj@kernel.org/

Thanks,
SJ

> ---
>  kernel/events/core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index b981b879bcd8..824c23830272 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -9759,6 +9759,7 @@ void perf_tp_event(u16 event_type, u64 count, void *record, int entry_size,
>  
>  	perf_sample_data_init(&data, 0, 0);
>  	data.raw = &raw;
> +	data.sample_flags |= PERF_SAMPLE_RAW;
>  
>  	perf_trace_buf_update(record, event_type);
>  
> -- 
> 2.28.0