linux-kernel - [BUG] perf stat: explicit grouping yields unexpected results

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 for Android: free password hash cracker in your pocket

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

Message-ID: <CABPqkBTiBHF4wZ3c_Czkh3JgvXGNWJW1LH42Jh4NG_ZJkGkbgw@mail.gmail.com>
Date:	Thu, 14 Nov 2013 21:50:49 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>, David Ahern <dsahern@...il.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Namhyung Kim <namhyung.kim@....com>
Subject: [BUG] perf stat: explicit grouping yields unexpected results

Jiri,

I was trying the grouping support in perf stat and I was surprised
to see that if I create a group that is too big to be scheduled, and
where only N out of P events can fit, perf stat still yields counts
for the N events. I was expecting 0 counts or <not supported>.

The kernel semantic is to schedule all the events in a group or none.
Perf does something different and this is confusing. If you use explicit
grouping then I think you want to group to fail if not all the events can
be scheduled:

On an IvyBridge:
$ perf stat --g -e
'{cycles,instructions,branches,branches,branches,branches,branches}'
noploop 1
     3 229 417 079 cycles
     3 223 919 023 instructions              #    1,00  insns per cycle
     3 220 868 098 branches
     3 220 868 098 branches
     3 220 868 098 branches
     3 220 868 098 branches
   <not supported> branches

I think it should be: <not supported> for all events.
--
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/