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] what happens when a PoD page is touched?

To: "Paul Durrant" <Paul.Durrant@xxxxxxxxxx>, "Tim Deegan" <Tim.Deegan@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] what happens when a PoD page is touched?
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Tue, 17 May 2011 09:39:34 +1000
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 16 May 2011 16:40:39 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <291EDFCB1E9E224A99088639C4762022B37FC178FA@xxxxxxxxxxxxxxxxxxxxxxxxx>
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: <AEC6C66638C05B468B556EA548C1A77D01D57078@trantor> <20110516083905.GP24068@xxxxxxxxxxxxxxxxxxxxxxx> <291EDFCB1E9E224A99088639C4762022B37FC178F9@xxxxxxxxxxxxxxxxxxxxxxxxx> <AEC6C66638C05B468B556EA548C1A77D01D570EB@trantor> <291EDFCB1E9E224A99088639C4762022B37FC178FA@xxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcwTpN+bajrHxxU3SuO3T+F6nhFaRAABS6hwAAApRtAAABGywAAdxYFw
Thread-topic: [Xen-devel] what happens when a PoD page is touched?
> 
> > -----Original Message-----
> >
> > I've not seen any slowdown on boot with any version of Windows until
> > I go to actually do the balloon down...
> >
> 
> In that case I guess your slowdown is caused by touching the pages.
IIRC you
> will encounter a sweep every time you touch a pod page and the cache
is
> exhausted. The sweep should reap all zeroed pages and hopefully fill
the cache
> so the sweep should not be invoked too often. Try using the
non-touching
> allocator.
> 

So avoiding the sweep is the thing to do then?

Where does the sweep start? Does it sweep in physical address order from
lowest address to highest? If I allocated some memory with a low
physical address and zero'd it and then didn't touch it would that be
found first?

Alternatively, I balloon down 1MB of memory at a time - if I could set
aside 1MB of memory that was filled with 0's and could somehow tell xen
to use that memory first then it might speed things up too yes?

Thanks

James

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