From: Ingo Molnar <mingo@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: acme@ghostprotocols.net, linux-kernel@vger.kernel.org,
peterz@infradead.org, Robert Richter <robert.richter@amd.com>
Subject: Re: [PATCH 3/3 v2] perf tool: give user better message if precise is not supported
Date: Fri, 14 Sep 2012 13:36:17 +0200 [thread overview]
Message-ID: <20120914113617.GA13299@gmail.com> (raw)
In-Reply-To: <50531151.9020202@gmail.com>
* David Ahern <dsahern@gmail.com> wrote:
> On 9/13/12 11:43 PM, Ingo Molnar wrote:
> >>v2: softened message to 'may not be' supported per Robert's suggestion
> >
> > Well, either it's supported on this machine or it's not -
> > why does the text have to be so unsure about it?
>
> Because EOPNOTSUPP is returned for more than just precise
> mode. We cannot say with certainty that the precise attribute
> caused that errno.
Well, then that is useful information we *lost*, and that
situation needs to be improved on the ABI side: an expanded
error code present in the event structure, copied back to
user-space on errors, or so.
(Alternatively, a special event channel just to pass back
expanded error conditions.)
Computers are supposed to make life easier for humans, by
answering such "what did go wrong?" questions. Our losing of
precise error conditions is a usability bug really - and in the
perf project we are in a unique position to be able to improve
both the kernel side code and make immediate use of it on the
tooling side as well.
Thanks,
Ingo
next prev parent reply other threads:[~2012-09-14 11:43 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-13 20:59 [PATCH 0/3 v3] perf: precise mode and exclude_guest David Ahern
2012-09-13 20:59 ` [PATCH 1/3] perf tool: precise mode requires exclude_guest David Ahern
2012-10-20 0:55 ` [tip:perf/urgent] perf tool: Precise " tip-bot for David Ahern
2012-09-13 20:59 ` [PATCH 2/3] perf: require exclude_guest to use PEBS - kernel side enforcement David Ahern
2012-10-20 0:56 ` [tip:perf/urgent] perf: Require " tip-bot for Peter Zijlstra
2012-09-13 20:59 ` [PATCH 3/3 v2] perf tool: give user better message if precise is not supported David Ahern
2012-09-14 5:43 ` Ingo Molnar
2012-09-14 11:13 ` David Ahern
2012-09-14 11:36 ` Ingo Molnar [this message]
2012-09-14 11:43 ` David Ahern
2012-09-14 18:00 ` Arnaldo Carvalho de Melo
2012-09-14 18:07 ` Peter Zijlstra
2012-09-14 20:05 ` Ingo Molnar
2012-09-14 20:11 ` Ingo Molnar
2012-09-14 21:26 ` Peter Zijlstra
2012-09-17 7:11 ` Ingo Molnar
2012-10-25 8:01 ` [tip:perf/core] perf tools: Give " tip-bot for David Ahern
2012-09-26 1:24 ` [PATCH 0/3 v3] perf: precise mode and exclude_guest David Ahern
2012-10-09 15:08 ` David Ahern
-- strict thread matches above, loose matches on Subject: below --
2012-09-12 15:16 [PATCH 0/3 v2] " David Ahern
2012-09-12 15:16 ` [PATCH 3/3 v2] perf tool: give user better message if precise is not supported David Ahern
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