linux-kernel - Re: [PATCH 08/11] perf/x86/intel: Add Intel Cache QoS Monitoring support

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]

Date:	Wed, 8 Oct 2014 22:51:14 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 08/11] perf/x86/intel: Add Intel Cache QoS Monitoring
 support

On Wed, Oct 08, 2014 at 04:47:04PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 08, 2014 at 01:15:35PM +0100, Matt Fleming wrote:
> > I was having an interesting discussion with one of the teams using this
> > stuff at Intel and they made the suggestion that when using,
> > 
> >   perf stat -p <pid>
> > 
> > we should by default opt for sharing an RMID between all tasks in that
> > thread group, rather that assigning a new RMID for each task, which is
> > what we do currently.
> > 
> > Right now, it's like the Oprah Winfrey of RMID assignment, "You get an
> > RMID, and you get an RMID!"
> > 
> > Which means we'll run out of RMIDs quicker, and enable the rotation code
> > sooner.
> > 
> > I'm wondering whether we should require that the user specify whether
> > they want per-thread monitoring if using -p, via some perf tools event
> > modifier, and make the record-per-thread-data scenario the exceptional
> > case, rather than the default?
> 
> Right so perf cannot do this. And I'm not sure that's fixable, it
> depends a bit on how the cqm thing deals with inherited events, IFF it
> can reuse RMIDs for inherited events we might be able to extend the
> syscall to install 'inherited' events throughout the process group,
> instead of just the one thread.

Right, so inherited events aren't going to work right for this. Look at
patch 10, these events target a different task and will not match, so
we'll not share RMIDs.

The only way to make this happen is stuff the process in a cgroup and
measure the cgroup.
--
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/