linux-kernel - Re: [PATCH 2/2] perf intel-pt: Refine kernel decoding only warning message

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Message-ID: <20200528143818.GH16490@kernel.org>
Date:   Thu, 28 May 2020 11:38:18 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH 2/2] perf intel-pt: Refine kernel decoding only warning
 message

Em Thu, May 28, 2020 at 03:08:59PM +0300, Adrian Hunter escreveu:
> Stop the message displaying when user space is not being traced.
> 
> Example:
> 
>   Prerequisites:
> 
>     sudo setcap "cap_sys_rawio,cap_sys_admin,cap_sys_ptrace,cap_syslog,cap_ipc_lock=ep" ~/bin/perf
>     sudo chmod +r /proc/kcore
> 
>   Before:
> 
>     $ perf record --no-switch-events --kcore -a -e intel_pt//k -- sleep 0.001
>     Warning:
>     Intel Processor Trace decoding will not be possible except for kernel tracing!
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 0.838 MB perf.data ]
> 
>   After:
> 
>     $ perf record --no-switch-events --kcore -a -e intel_pt//k -- sleep 0.001
>     [ perf record: Woken up 1 times to write data ]
>     [ perf record: Captured and wrote 1.068 MB perf.data ]
> 
>     $ sudo chmod go-r /proc/kcore
>     $ sudo setcap -r ~/bin/perf

Thanks, tested as root and applied.

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/arch/x86/util/intel-pt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
> index 3fc547769707..9fb137282dc8 100644
> --- a/tools/perf/arch/x86/util/intel-pt.c
> +++ b/tools/perf/arch/x86/util/intel-pt.c
> @@ -879,7 +879,8 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
>  	 * per-cpu with no sched_switch (except workload-only).
>  	 */
>  	if (!ptr->have_sched_switch && !perf_cpu_map__empty(cpus) &&
> -	    !target__none(&opts->target))
> +	    !target__none(&opts->target) &&
> +	    !intel_pt_evsel->core.attr.exclude_user)
>  		ui__warning("Intel Processor Trace decoding will not be possible except for kernel tracing!\n");
>  
>  	return 0;
> -- 
> 2.17.1
> 

-- 

- Arnaldo