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Message-ID: <20090126221038.GA7440@elte.hu>
Date: Mon, 26 Jan 2009 23:10:38 +0100
From: Ingo Molnar <mingo@...e.hu>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Andrew Morton <akpm@...ux-foundation.org>,
Papi <ptools-perfapi@...utk.edu>,
"David S. Miller" <davem@...emloft.net>,
Mike Galbraith <efault@....de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Eric Dumazet <dada1@...mosbay.com>,
Paul Mackerras <paulus@...ba.org>, Peter Anvin <hpa@...or.com>,
"eranian@...il.com" <eranian@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
"perfmon2-devel@...ts.sourceforge.net"
<perfmon2-devel@...ts.sourceforge.net>,
Arjan van de Ven <arjan@...radead.org>
Subject: Re: [perfmon2] [announce] Performance Counters for Linux, v6
* Luck, Tony <tony.luck@...el.com> wrote:
> > - or the PMU capability is expressed as a special counter type (if it's
> > useful enough) - and then either the write() method or ioctl is extended
> > to express attributes we want to set/change while a counter is running.
>
> The product of:
> {exotic PMU modes} * {creative performance measurement ideas}
>
> will produce a large number of candidates for these special counters (at
> least on ia64 ... which has a large number of exotic PMU options).
>
> I don't think that I'm qualified to judge which of them are "useful
> enough" to warrant a special counter type.
it should certainly be done on a case by case basis. They need to be
consciously exposed not just summarily exported to user-space, because PMU
hw features have security implications so it has to be done all
explicitly.
Ingo
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