Received-SPF: pass (google.com: domain of linux-kernel+bounces-177824-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Precedence: bulk
MIME-Version: 1.0
References: <20240502213507.2339733-1-irogers@google.com> <20240502213507.2339733-3-irogers@google.com>
 <fe41f9a7-5726-49d5-9bc6-70102d9680a1@infradead.org>
In-Reply-To: <fe41f9a7-5726-49d5-9bc6-70102d9680a1@infradead.org>
From: Ian Rogers <irogers@google.com>
Date: Mon, 13 May 2024 09:22:57 -0700
Message-ID: <CAP-5=fWHrX5AgH8=62f3=a-SSqUACXX1rkDZJ-WV1RcNieeHFA@mail.gmail.com>
Subject: Re: [PATCH v5 2/6] perf Document: Sysfs event names must be lower or
 upper case
To: Randy Dunlap <rdunlap@infradead.org>
Cc: Kan Liang <kan.liang@linux.intel.com>, Thomas Richter <tmricht@linux.ibm.com>, 
	Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, 
	Arnaldo Carvalho de Melo <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, 
	Mark Rutland <mark.rutland@arm.com>, 
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, 
	Bjorn Helgaas <bhelgaas@google.com>, Jonathan Corbet <corbet@lwn.net>, 
	Jing Zhang <renyu.zj@linux.alibaba.com>, James Clark <james.clark@arm.com>, 
	Ravi Bangoria <ravi.bangoria@amd.com>, linux-kernel@vger.kernel.org, 
	linux-perf-users@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Sun, May 12, 2024 at 3:08=E2=80=AFPM Randy Dunlap <rdunlap@infradead.org=
> wrote:
>
> Hi,
>
> On 5/2/24 2:35 PM, Ian Rogers wrote:
> > To avoid directory scans in perf it is going to be assumed that sysfs
> > event names are either lower or upper case.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
> > ---
> >  .../ABI/testing/sysfs-bus-event_source-devices-events       | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-bus-event_source-devices-e=
vents b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> > index 77de58d03822..e7efeab2ee83 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> > +++ b/Documentation/ABI/testing/sysfs-bus-event_source-devices-events
> > @@ -37,6 +37,12 @@ Description:       Per-pmu performance monitoring ev=
ents specific to the running syste
> >               performance monitoring event supported by the <pmu>. The =
name
> >               of the file is the name of the event.
> >
> > +             As performance monitoring event names are case
> > +             insensitive in the perf tool, the perf tool only looks
> > +             for lower or upper case event names in sysfs to avoid
> > +             scanning the directory. It is therefore required the
> > +             name of the event here is either lower or upper case.
> > +
>
> This is ambiguous to me. Is it clear to everyone else?
>
> "for lower or upper case event names":
>
> Is that a logical OR or an exclusive OR?
> "AbC" contains lower case or upper case characters. :)
>
> I think the code [static bool permitted_event_name()]
> implements an exclusive OR.
> The code also allows event names to contain numbers AFAICT.
> The documentation doesn't mention this.
>
> HTH.
>
> >               File contents:
> >
> >                       <term>[=3D<value>][,<term>[=3D<value>]]...

Sorry, this reads like a troll. Assuming good intentions, could you
propose a fix in the form of a patch? When a word is made upper or
lower case I believe it is generally assumed the operation applies to
all characters within the word, but I'm happy to see ambiguity cleared
up.

Thanks,
Ian

> --
> #Randy
> https://people.kernel.org/tglx/notes-about-netiquette
> https://subspace.kernel.org/etiquette.html