WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] VM start time slows with large number of VMs

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] VM start time slows with large number of VMs
From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Date: Wed, 5 Sep 2007 18:37:32 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, "Carb, Brian A" <Brian.Carb@xxxxxxxxxx>
Delivery-date: Wed, 05 Sep 2007 10:38:03 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <C304A1BA.D3AD%Keir.Fraser@xxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <089B0D75973E1241B941D0A9854F23FC08E17469@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <C304A1BA.D3AD%Keir.Fraser@xxxxxxxxxxxx>
Reply-to: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.4.1i
On Wed, Sep 05, 2007 at 06:11:06PM +0100, Keir Fraser wrote:
> xenstore slowness seems a reasonable hypothesis. How does performance of
> ?time xenstore-ls >/dev/null¹ change as you increase the number of guests?

There's another issue with the way hotplug scripts do locking which exhbits
fairly pathelogical behaviour when a large number of guests are started 
concurrently. We've got a patch we're evaluating which changes  the use of
lock files + looping + sleeps, to instead use the 'flock' shell util.

I suspect the performance issues will be a combination of both the locking stuff
and the xenstore I/O. You might also want to try putting /var/lib/xenstored
onto tmpfs eg in  initscripts before xenstored starts ...

  mkdir /dev/shm/xenstored
  mount --bind /dev/shm/xenstored /var/lib/xenstored


Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=| 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel