From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: Populate-on-demand memory problem Date: Mon, 09 Aug 2010 09:48:33 +0100 Message-ID: <4C5FDD01020000780000EC9E@vpn.id2.novell.com> References: <201007270948.44604.dietmar.hahn@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: George Dunlap , xen-devel@lists.xensource.com, Dietmar Hahn List-Id: xen-devel@lists.xenproject.org Keir, with Dietmar having tested this successfully, is there anything that keeps this from being applied to -unstable (and perhaps also 4.0.1)? Jan >>> On 27.07.10 at 15:10, George Dunlap = wrote: > Hmm, looks like I neglected to push a fix upstream. Can you test it > with the attached patch, and tell me if that fixes your problem? >=20 > -George >=20 > On Tue, Jul 27, 2010 at 8:48 AM, Dietmar Hahn > wrote: >> Hi list, >> >> we ported our system from Novel SLES11 using xen-3.3 to SLES11 SP1 = using >> xen-4.0 and ran into some trouble with the pod stuff. >> We have a HVM guest and already used target_mem < max_mem on startup of >> the guest. >> With the new xen version we get >> (XEN) p2m_pod_demand_populate: Out of populate-on-demand memory! = tot_pages=20 > 792792 pod_entries 800 >> I did some code revisions and looking at pod patches >> (http://lists.xensource.com/archives/html/xen-devel/2008-12/msg01030.htm= l) >> to understand the behavior. We use the following configuration: >> maxmem =3D 4096 >> memory =3D 3096 >> What I see is: >> - our guest boots with e820 map showing maxmem. >> - reading xenstore memory/target returns '3170304' means 3096MB, = 792576=20 > pages >> Now our guest uses the target memory and gives back 1000MB via >> hypervisor call XENMEM_decrease_reservation to the hypervisor. >> >> Later I try to map the complete domU memory into dom0 kernel space and = here=20 > I >> get the 'Out of populate-on-demand memory' crash. >> >> As far as I understand (ignoring the p2m_pod_emergency_sweep) >> - on populating a page >> - the page is taken from the pod cache >> - p2md->pod.count-- >> - p2md->pod.entry_count-- >> - page gets type p2m_ram_rw >> - decreasing a page >> - p2md->pod.entry_count-- >> - page gets type p2m_invalid >> >> So if the guest uses all the target memory and gave back all >> the (maxmem-target) memory p2md->pod.count and p2md->pod.entry_count = should be >> zero. >> I added some tracing in the hypervisor and see on start of the guest: >> p2m_pod_set_cache_target: p2md->pod.count: 791264 tot_pages: 791744 >> This pod.count is lower then the target seen in the guest! >> On the first call of p2m_pod_demand_populate() I can see >> p2m_pod_demand_populate: p2md->pod.entry_count: 1048064 p2md->pod.count:= 791264=20 > tot_pages: 792792 >> So pod.entry_count=3D1048064 (4096MB) complies to maxmem but >> pod.count=3D791264 is lower then the target memory in xenstore. >> >> Any help is welcome! >> Thanks. >> Dietmar. >> >> -- >> Company details: http://ts.fujitsu.com/imprint.html=20 >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com=20 >> http://lists.xensource.com/xen-devel=20 >>