From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] KVM: s390: remove delayed reallocation of page tables for KVM Date: Thu, 23 Apr 2015 14:07:07 +0200 Message-ID: <5538E06B.8090507@redhat.com> References: <1429787297-9292-1-git-send-email-borntraeger@de.ibm.com> <1429787297-9292-2-git-send-email-borntraeger@de.ibm.com> <2E97DEE6-47EA-484A-9F02-9F031DCA8F36@suse.de> <5538DAD4.4060505@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: KVM , Cornelia Huck , Jens Freimann , Martin Schwidefsky , Cole Robinson To: Christian Borntraeger , Alexander Graf Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48350 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965241AbbDWMHN (ORCPT ); Thu, 23 Apr 2015 08:07:13 -0400 In-Reply-To: <5538DAD4.4060505@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 23/04/2015 13:43, Christian Borntraeger wrote: >> > >> > Couldn't you make this a hidden kconfig option that gets automatically selected when kvm is enabled? Or is there a non-kvm case that needs it too? > For things like RHEV the default could certainly be "enabled", but for normal > distros like SLES/RHEL, the idea was to NOT enable that by default, as the non-KVM > case is more common and might suffer from the additional memory consumption of > the page tables. (big databases come to mind) > > We could think about having rpms like kvm to provide a sysctl file that sets it if we > want to minimize the impact. Other ideas? I can say what _won't_ work which is tying it to the KVM module. Nowadays it is loaded automatically via udev on the first /dev/kvm access, and that's already too late because qemu-kvm's page tables have been created already. Right? With my Fedora hat on, adding a sysctl file to the userspace RPMs (e.g. qemu) would work. CCing Cole Robinson who is the main maintainer of the Fedora virt packages. Paolo