linux-kernel - Re: [RFC PATCHv3] perf tools: add event grouping capability to "perf stat"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1290694348.2145.37.camel@laptop>
Date:	Thu, 25 Nov 2010 15:12:28 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Julia Lawall <julia@...u.dk>, Tom Zanussi <tzanussi@...il.com>,
	linux-kernel@...r.kernel.org, Matt Fleming <matt@...sole-pimps.org>
Subject: Re: [RFC PATCHv3] perf tools: add event grouping capability to
 "perf stat"

On Thu, 2010-11-25 at 15:07 +0100, Stephane Eranian wrote:
> On Thu, Nov 25, 2010 at 3:02 PM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> > On Thu, 2010-11-25 at 14:19 +0100, Stephane Eranian wrote:
> >
> >> I think using PERF_SAMPLE_READ may expose a problem in the
> >> perf.data format. To correctly parse a sample created with SAMPLE_READ,
> >> you need to know the attr.read_format. But for that you need to know the
> >> event which caused the sample, but for that you need the SAMPLE_ID,
> >> and you don't know if it's there or not. In other words, there is a chicken
> >> and egg problem.
> >>
> >> I think the issue is that PERF_RECORD_SAMPLE is missing a mandatory
> >> piece of information: overflow event ID. This must a mandatory field, not
> >> optional as it is today. It is okay when you have only one group, but we'd
> >> like to go beyond that.
> >
> >
> >
> > I'm not sure I get it, there's both PERF_FORMAT_ID and PERF_SAMPLE_ID,
> > so afaict there's a working combination for what you want to do.
> >
> Ok, I had forgotten about PERF_SAMPLE_ID. But that means that if the
> number of groups > 1, then if you use PERF_SAMPLE_READ, you MUST
> also use PERF_SAMPLE_ID. Otherwise you cannot get back to the event
> that generated the sample and thus attr.read_format.

perf-record already does that:

        if (nr_counters > 1)
                attr->sample_type |= PERF_SAMPLE_ID;



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/