From mboxrd@z Thu Jan  1 00:00:00 1970
From: robert.richter@amd.com (Robert Richter)
Date: Wed, 10 Mar 2010 16:01:21 +0100
Subject: [PATCH 4/6] perf-events: export enable/disable event symbols
	to kernel modules
In-Reply-To: <1268231442.5279.1.camel@twins>
References: <1268217690-29712-1-git-send-email-will.deacon@arm.com>
	<1268217690-29712-2-git-send-email-will.deacon@arm.com>
	<1268217690-29712-3-git-send-email-will.deacon@arm.com>
	<1268217690-29712-4-git-send-email-will.deacon@arm.com>
	<1268217690-29712-5-git-send-email-will.deacon@arm.com>
	<1268218566.8991.1.camel@twins>
	<001201cac047$70b71c60$52255520$@deacon@arm.com>
	<1268231442.5279.1.camel@twins>
Message-ID: <20100310150121.GA1585@erda.amd.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 10.03.10 15:30:42, Peter Zijlstra wrote:
> On Wed, 2010-03-10 at 11:47 +0000, Will Deacon wrote:
> > Hello Peter,
> > 
> > > On Wed, 2010-03-10 at 10:41 +0000, Will Deacon wrote:
> > > > The perf_event_enable and perf_event_disable functions are used to
> > > > control the activation of perf-events for a given context or CPU.
> > > >
> > > > This patch exports these symbols so that they can be used by kernel
> > > > modules. Without these symbols, an event must be destroyed and recreated
> > > > to disable or enable it respectively. The maximum number of perf-events
> > > > is also made available to modules via the perf_get_max_events function.
> > > 
> > > Where is the module that uses all this?
> > 
> > It's part of the same patchset:
> > 
> > http://lists.infradead.org/pipermail/linux-arm-kernel/2010-March/011126.html
> > 
> > The idea is to use perf-events as the backend for OProfile to avoid replicating
> > the PMU accessor code.
> 
> Ah, very nice. Can something like that be done in general, like an
> arch-independent oprofile backend using perf, or is there too much
> arch-specific bits to the oprofile stuff?
> 
> I know Robert talked about doing something like this, I just have no
> clue how arch specific this would be.

Thanks for cc'ing me. I like this approach. Will take a look at the
patches.

Yes, for implementing oprofile on top of perf we have to touch every
architecture separately to be backward compatible.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter at amd.com