From mboxrd@z Thu Jan  1 00:00:00 1970
From: Glauber Costa <gcosta@redhat.com>
Subject: Re: [PATCH 0/8] RFC: vcpu pinning at qemu start
Date: Wed, 05 Mar 2008 10:10:23 -0300
Message-ID: <47CE9BBF.6090408@redhat.com>
References: <12046477213193-git-send-email-gcosta@redhat.com>
	<47CD8A02.50402@codemonkey.ws> <47CD907E.1080607@redhat.com>
	<47CDA2D8.7060709@codemonkey.ws> <47CDAA08.3030006@redhat.com>
	<47CE16EC.8040603@codemonkey.ws>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: kvm-devel@lists.sourceforge.net, chrisw@sous-sol.org,
	avi@qumranet.com
To: Anthony Liguori <anthony@codemonkey.ws>
Return-path: <kvm-devel-bounces@lists.sourceforge.net>
In-Reply-To: <47CE16EC.8040603@codemonkey.ws>
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

Anthony Liguori wrote:
> Glauber Costa wrote:
>> Anthony Liguori wrote:
>>
>> No, it can't. Because at the time qemu starts, no vcpu -> thread id 
>> relationship exists at all. And we don't know when it will.
> 
> Sure we do.  The vcpu -> thread id relationship is valid after 
> kvm_init_ap() is called which is after machine init but before the 
> select loop is entered for the first time.  Therefore, if you start qemu 
> with -S, then connect on the monitor, and do an info cpus, you could be 
> guaranteed to be told the mapping.

I missed that. This changes everything. I now completely agree with you.

I'll post patches that expose the relationship, if it's better.

> The threads are *idle* at this point so there's no harm if they were 
> started on the "wrong" CPU.  You can now taskset to your hearts content 
> and then when you're happy with placement, you can issue a 'cont' so 
> that the VM actually starts running.  I saw "wrong" because you can 
> still taskset the initial creation guaranteeing that the threads are 
> created on the right group of physical CPUs, you just can't specify the 
> exact mapping until you start interacting with the monitor.
> 
> Regards,
> 
> Anthony Liguori
> 
>>> Regards,
>>>
>>> Anthony Liguori
>>>
>>>>
>>>>
>>>
>>
> 


-------------------------------------------------------------------------
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/