linux-kernel - Re: [PATCH] perf/script: remove extraneous newline in perf_sample__fprintf

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Message-ID: <CABPqkBQakhL_zm+4Dt0y3hFcQ7iBh1H31HwyvfnH4kDa2M94SQ@mail.gmail.com>
Date:   Wed, 29 Apr 2020 19:13:01 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>, mingo@...e.hu,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>, Ian Rogers <irogers@...gle.com>,
        "Liang, Kan" <kan.liang@...el.com>
Subject: Re: [PATCH] perf/script: remove extraneous newline in perf_sample__fprintf_regs()

On Wed, Apr 29, 2020 at 7:09 PM Andi Kleen <ak@...ux.intel.com> wrote:
>
> > I was under the impression that perf script was generating one line
> > per sample. Otherwise, seems hard to parse.
>
> That's only true for simple cases. A lot of the extended output options
> have long generated multiple lines. And of course call stacks always did.
>
> > Could you give me the cmdline options of perf script that justify the newline.
>
> e.g.  perf script -F iregs,uregs
>
But then it should only use the \n when needed.
It is a bit like perf stat printing cgroup as "" when not using cgroup
mode add a bunch of white spaces/tab at the end of the line for
nothing.

I also suggest that we improve perf stat/script output with an output
format that is easier to parse, such as JSON with name: value pairs.
that would avoid all these \n and
flaky parsing regexp or script I have seen, even internally.

> -Andi