From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@qumranet.com>
Subject: Re: [RFC] Performance monitoring units and KVM
Date: Tue, 19 Feb 2008 18:05:51 +0200
Message-ID: <47BAFE5F.9060409@qumranet.com>
References: <200802162304.43141.balajirrao@gmail.com>
	<87ejbaxdes.fsf@pike.pond.sub.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: kvm-devel@lists.sourceforge.net, balbir@in.ibm.com,
	Balaji Rao <balajirrao@gmail.com>
To: Markus Armbruster <armbru@redhat.com>
Return-path: <kvm-devel-bounces@lists.sourceforge.net>
In-Reply-To: <87ejbaxdes.fsf@pike.pond.sub.org>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/kvm-devel>,
	<mailto:kvm-devel-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=kvm-devel>
List-Post: <mailto:kvm-devel@lists.sourceforge.net>
List-Help: <mailto:kvm-devel-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/kvm-devel>,
	<mailto:kvm-devel-request@lists.sourceforge.net?subject=subscribe>
Sender: kvm-devel-bounces@lists.sourceforge.net
Errors-To: kvm-devel-bounces@lists.sourceforge.net
List-Id: kvm.vger.kernel.org

Markus Armbruster wrote:
> Balaji Rao <balajirrao@gmail.com> writes:
>
>   
>> Hi all!
>>
>> Earlier it was suggested that we go ahead with emulating Perf Mon Events in 
>> exposing it to the guest. The serious limitation in this approach is that we 
>> end up exposing only a small number of events to the guest, even though the 
>> host hardware is capable of much more. The only benefit this approach offers is 
>> that, it doesn't break live migration.
>>
>> The other option is to pass through the real PMU to the guest. I believe this 
>> approach is far better in the sense that,
>>     
>
> Do we really have an either/or alternative here?
>
>   

I think that PMU pass through makes more sense, due to the nature of 
existing non-paravirtualized tools.

> There are ways to use the PMU in guests that don't require costly
> virtualization of the real PMU.  They put the guest's performance
> monitoring interface at a level higher than hardware PMU.
>   

On the other hand, they will work only on very new guests.  Paravirt pmu 
makes sense, but it cannot replace the hardware pmu interface.


-- 
error compiling committee.c: too many arguments to function


-------------------------------------------------------------------------
This SF.net email is sponsored by: Microsoft
Defy all challenges. Microsoft(R) Visual Studio 2008.
http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/