linux-kernel - Re: [PATCH] perf: Fix "Track with sched_switch" test by not printing warnings in quiet mode

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Date:   Mon, 17 Oct 2022 09:33:34 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     James Clark <james.clark@....com>
Cc:     Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] perf: Fix "Track with sched_switch" test by not printing
 warnings in quiet mode

Em Fri, Oct 14, 2022 at 10:47:34AM +0100, James Clark escreveu:
> On 13/10/2022 17:57, Namhyung Kim wrote:
> > On Wed, Oct 12, 2022 at 10:12 AM James Clark <james.clark@....com> wrote:
> >> On 12/10/2022 17:50, Namhyung Kim wrote:
> >>> On Wed, Oct 12, 2022 at 4:13 AM James Clark <james.clark@....com> wrote:
> >>>>> The test already supplies -q to run in quiet mode, so extend quiet mode
> >>>>> to perf_stdio__warning() and also ui__warning() for consistency.
> >>>
> >>> I'm not sure if suppressing the warnings with -q is a good thing.
> >>> Maybe we need to separate warning/debug messages from the output.
> >>
> >> I don't see the issue with warnings being suppressed in quiet mode as
> >> long as errors are still printed. In other cases warnings have already
> >> been suppressed by quiet mode and this site is the odd one out.
> >>
> >> What use case are you thinking of where someone explicitly adds -q but
> >> wants to see non fatal warnings?
> > 
> > I don't have any specific use case.  If it's already suppressed in other
> > cases, I'm fine with it.
> > 
> 
> Actually I may have been mistaken. Seems like quiet is only used for
> "extra info" type messages rather than warnings. Although the commit
> message does say:
> 
>   The -q/--quiet option is to suppress any message. Sometimes users just
>   want to see the numbers and it can be used for that case.
> 
> With 'any' that I would take to include warnings as well. I could move
> warnings to stderr, but this has a much greater chance of breaking
> anyone's workflows that might be looking for warnings on stdout than
> removing warnings when -q is provided.
> 
> Also if warnings are moved to stderr and quiet isn't used, there would
> be no way to suppress warnings in the TUI which might actually be a
> useful feature.
> 
> So I'm still leaning towards the original change, if you are ok with
> that even though it's not done elsewhere?

Namhyung? I tend to agree with James.

- Arnaldo