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] [PATCH] xen: Implement domain runstates

To: Keir Fraser <keir@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xen: Implement domain runstates
From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Date: Fri, 26 Nov 2010 11:52:52 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Bruce Edge <bruce.edge@xxxxxxxxx>
Delivery-date: Fri, 26 Nov 2010 03:53:54 -0800
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:cc:content-type; bh=oVRM7DTo91cwj4cwT7fKhWSJi3H4nzHyFdx6uDKFlp8=; b=dd9VG6AgSH9WGIqvOtBzKs6Qj/Sf2tseSiBd1EC6Whj3cKSqQwpG9AQ9GLYN4V1EhP jYkR92CxSzw8HTPC+4iAKY5HR1cf2And3pR35ic4Wi2rxiyN2dAX0YHFaGjhHZh8GWSv OwLttPXIiXC6rOQwTSaphNzkzXPbFrnqsovbk=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=Wy4kdBK5k47WpLrkqeKgVqs6pAMy2H+93C8wUCWXusTRwBqMcxCE2fObmqDbd1ueGL 3vtNwNiv3n2ryp+YVmrHSfXpe2pnnWc6Mv7b8AfOS3Dj+Fo+UN2yX2jDIqIqUxETIidb QxMX/waiWCkiF0YkVfIYtBTlWW9hOSaTj+OM0=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <C91492B6.B228%keir@xxxxxxx>
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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <AANLkTi=xA9dMkS+p2G3MxTTGvFqOYNjoFKd8hCac9jBn@xxxxxxxxxxxxxx> <C91492B6.B228%keir@xxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Thu, Nov 25, 2010 at 10:24 PM, Keir Fraser <keir@xxxxxxx> wrote:
> You may be under the impression the feature is free. It isn't -- it adds a
> lock and loop over all vcpus on every vcpu scheduling/descheduling decision.
> That could be frequent for VCPUs doing a lot of short blocking, for example.
> And the system-wide work done to support this feature will scale
> quadratically on average with vcpus-per-domain. My gut feeling is this isn't
> a good thing to have on your context switch path.

That's certainly reasonable.  If I get a chance to do some perf
testing over the next few weeks, I'll post some performance numbers,
and we can quantify the slowdown (although catching potential cache
"cliffs" may be more difficult).

Would you consider accepting it as a feature off by default, enabled
by a Xen command-line parameter?

 -George

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