From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: xen pv hugepages Date: Fri, 7 Feb 2014 10:34:15 -0500 Message-ID: <20140207153415.GC3605@phenom.dumpdata.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Elena Ufimtseva Cc: "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On Thu, Feb 06, 2014 at 07:12:24PM -0500, Elena Ufimtseva wrote: > On Thu, Feb 6, 2014 at 6:59 PM, Konrad Rzeszutek Wilk > wrote: > > On February 6, 2014 5:17:44 PM EST, Elena Ufimtseva wrote: > >>Hello > >> > >>As I can see there is no support for hugepages in Xen for PV kernels. > >>Is this something in the future plans or there is no really need to > >>have this implemented? > > > > It was implemented. The UEK2 kernel (Oracle's) and SLES (I think) has this implemented. But making it upstream means adding some Xen specific code in the generic code which is a no-go. > > > > If you use PVH you get it for free. With the patches that Mukesh posted to enable some cpuid flags I was able to boot a guest with 2MB and 1GB pages without any trouble. > > Ok, I see. Well, I would think then that the kernel then should not > provide any possibility to use it? Otherwise there are oopses and some > other unpleasant things happening when trying to use huge pages. I am > not sure, maybe if its clearly states that there is no hugetlb support > for pv, then there is no need for this? I was under the impression that the hugetlb option only gets enabled if the 'cpu_has_pse' bit is set. And for PV that is cleared so it won't be set. > > >> > >>I came across this paper > >>https://www.kernel.org/doc/ols/2011/ols2011-gadre.pdf, > >>not sure if this was somehow presented to xen community, I can't find > >>any code related to this. > >> > >>Thank you! > > > > > > > > -- > Elena