linux-kernel - Re: [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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <alpine.DEB.2.02.1311151007340.15200@pianoman.cluster.toy>
Date:	Fri, 15 Nov 2013 10:08:45 -0500 (EST)
From:	Vince Weaver <vince@...ter.net>
To:	Ingo Molnar <mingo@...nel.org>
cc:	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	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: Re: [BUG] perf stat: explicit grouping yields unexpected results

On Fri, 15 Nov 2013, Ingo Molnar wrote:
> 
> Btw., does the kernel side currently support discovery of such 
> impossible group scheduling constraints at group setup time? If not 
> then it probably should and it should reject them straight away.

It does not, or at least I'm pretty sure it can't if the NMI watchdog is 
enabled (Stephane, are you doing your tests with NMI watchdog disabled?)

This is a big problem with PAPI.  If the NMI watchdog is enabled you can't 
tell if a group will fail until the first read, the kernel can't tell you 
at setup time.

Vince
--
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/