From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1Iu9PA-0003Ma-9Q
	for qemu-devel@nongnu.org; Mon, 19 Nov 2007 11:23:24 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1Iu9P9-0003MO-PE
	for qemu-devel@nongnu.org; Mon, 19 Nov 2007 11:23:24 -0500
Received: from [199.232.76.173] (helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Iu9P9-0003MJ-L6
	for qemu-devel@nongnu.org; Mon, 19 Nov 2007 11:23:23 -0500
Received: from smtp.citrix.com ([66.165.176.89])
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <samuel.thibault@labri.fr>) id 1Iu9P9-0002WX-CQ
	for qemu-devel@nongnu.org; Mon, 19 Nov 2007 11:23:23 -0500
Date: Mon, 19 Nov 2007 16:23:19 +0000
From: Samuel Thibault <samuel.thibault@eu.citrix.com>
Subject: Re: [Qemu-devel] Re: memory usage and ioports
Message-ID: <20071119162319.GJ6331@implementation.uk.xensource.com>
References: <20071119152016.GE6331@implementation.uk.xensource.com>
	<20071119153421.GH6331@implementation.uk.xensource.com>
	<200711191617.27138.paul@codesourcery.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <200711191617.27138.paul@codesourcery.com>
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org

Paul Brook, le Mon 19 Nov 2007 16:17:26 +0000, a écrit :
> On Monday 19 November 2007, Samuel Thibault wrote:
> > Samuel Thibault, le Mon 19 Nov 2007 15:20:16 +0000, a écrit :
> > > Qemu currently uses 6 65k tables of pointers for handling ioports, which
> > > makes 3MB on 64bit machines. There's a comment that says "XXX: use a two
> > > level table to limit memory usage". But wouldn't it be more simple and
> > > effective to just allocate them through mmap() and when a NULL pointer
> > > is read, call the default handlers?
> >
> > For the ioport_opaque array (500KB on 64bit), it's much simpler, as the
> > attached patch suggests.
> 
> AFAICS This makes absolutely no difference to memory usage.

Ah, sorry, in a unix environment it doesn't indeed.  In an embedded
environment or so which has to provide a fully allocated bss because it
doesn't have cow support early enough, that makes a difference.

Samuel