From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753279AbaHBAwy (ORCPT ); Fri, 1 Aug 2014 20:52:54 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:46115 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbaHBAww (ORCPT ); Fri, 1 Aug 2014 20:52:52 -0400 Message-ID: <53DC3660.6050104@gmail.com> Date: Fri, 01 Aug 2014 17:52:48 -0700 From: Matthew Rushton User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Boris Ostrovsky , Matt Wilson , David Vrabel CC: konrad.wilk@oracle.com, msw@amazon.com, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, Matt Rushton Subject: Re: [PATCH v2 2/2] xen/setup: Remap Xen Identity Mapped RAM References: <1405814495-10868-1-git-send-email-mrushton@amazon.com> <1405814495-10868-2-git-send-email-mrushton@amazon.com> <53DA805D.4020300@citrix.com> <53DBA9AC.8000302@citrix.com> <20140801155206.GA13865@u109add4315675089e695.ant.amazon.com> <53DBB8BA.3030909@oracle.com> In-Reply-To: <53DBB8BA.3030909@oracle.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/01/14 08:56, Boris Ostrovsky wrote: > On 08/01/2014 11:52 AM, Matt Wilson wrote: >> On Fri, Aug 01, 2014 at 03:52:28PM +0100, David Vrabel wrote: >>> On 31/07/14 18:43, David Vrabel wrote: >>>> On 20/07/14 01:01, Matt Rushton wrote: >>>>> Instead of ballooning up and down dom0 memory this remaps the >>>>> existing mfns >>>>> that were replaced by the identity map. The reason for this is >>>>> that the >>>>> existing implementation ballooned memory up and and down which >>>>> caused dom0 >>>>> to have discontiguous pages. In some cases this resulted in the >>>>> use of bounce >>>>> buffers which reduced network I/O performance significantly. This >>>>> change will >>>>> honor the existing order of the pages with the exception of some >>>>> boundary >>>>> conditions. >>>>> >>>>> To do this we need to update both the Linux p2m table and the Xen >>>>> m2p table. >>>>> Particular care must be taken when updating the p2m table since >>>>> it's important >>>>> to limit table memory consumption and reuse the existing leaf >>>>> pages which get >>>>> freed when an entire leaf page is set to the identity map. To >>>>> implement this, >>>>> mapping updates are grouped into blocks with table entries getting >>>>> cached >>>>> temporarily and then released. >>>>> >>>>> On my test system before: >>>>> Total pages: 2105014 >>>>> Total contiguous: 1640635 >>>>> >>>>> After: >>>>> Total pages: 2105014 >>>>> Total contiguous: 2098904 >>>> Applied to devel/for-linus-3.17 >>> Unfortunately, this produces too many WARNINGs on some boxes or >>> with certain configurations. >> Hi David, >> >> Do you have more information about the systems or configurations that >> showed a problem? >> > > > This appears to be happening on 32-bit dom0. > > -boris It's unclear to me why the m2p update would be failing in this case (on first attempt) which causes the subsequent errors. I'll try to repro on a 32-bit dom0.