linux-kernel - Re: [PATCH v2] perf/sdt: Show proper hint

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Message-ID: <20170207155005.GC4222@redhat.com>
Date:   Tue, 7 Feb 2017 13:50:05 -0200
From:   Arnaldo Carvalho de Melo <acme@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        alexis.berlemont@...il.com, peterz@...radead.org,
        alexander.shishkin@...ux.intel.com, mpe@...erman.id.au,
        naveen.n.rao@...ux.vnet.ibm.com, mhiramat@...nel.org,
        maddy@...ux.vnet.ibm.com
Subject: Re: [PATCH v2] perf/sdt: Show proper hint

Em Tue, Feb 07, 2017 at 08:53:56AM +0100, Ingo Molnar escreveu:
> 
> * Arnaldo Carvalho de Melo <acme@...hat.com> wrote:
> 
> > Em Fri, Feb 03, 2017 at 03:56:42PM +0530, Ravi Bangoria escreveu:
> > > After patch:
> > >   $ perf record -a -e sdt_glib:idle__add
> > >     event syntax error: 'sdt_glib:idle__add'
> > >                          \___ unknown tracepoint
> > > 
> > >     Error: File /sys/kernel/debug/tracing/events/sdt_glib/idle__add not found.
> > >     Hint:  SDT event cannot be directly recorded on. Please use 'perf probe sdt_glib:idle__add' before recording it.
> > >     ...
> > > 
> > >   $ perf probe sdt_glib:idle__add
> > >     Added new event:
> > >       sdt_glib:idle__add   (on %idle__add in /usr/lib64/libglib-2.0.so.0.5000.2)
> > > 
> > >     You can now use it in all perf tools, such as:
> > > 
> > >         perf record -e sdt_glib:idle__add -aR sleep 1
> > > 
> > >   $ perf record -a -e sdt_glib:idle__add
> > >     [ perf record: Woken up 1 times to write data ]
> > >     [ perf record: Captured and wrote 0.175 MB perf.data ]
> > 
> > Looks much better! Thanks!
> > 
> > Unsure if we should state somewhere that this needs to be done only once
> > per boot.
> > 
> > Ingo, are you ok now? Ack?
> 
> Yeah, looks perfect to me!
> 
> Acked-by: Ingo Molnar <mingo@...nel.org>

Thanks, added that "first" and split the Hint line in two.

Automagically setting it up, doing the perf probe and rendering the
above comment irrelevant remains as a task to be performed.

- Arnaldo