From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: performance with guests running 2.4 kernels (specifically RHEL3) Date: Wed, 30 Apr 2008 14:56:11 +0100 Message-ID: <20080430135611.GL15421@redhat.com> References: <480C5C39.4040300@qumranet.com> <480E492B.3060500@cisco.com> <480EEDA0.3080209@qumranet.com> <480F546C.2030608@cisco.com> <481215DE.3000302@cisco.com> <20080428181550.GA3965@dmt> <4816617F.3080403@cisco.com> <4817F30C.6050308@cisco.com> <48184228.2020701@qumranet.com> <481876A9.1010806@cisco.com> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel , Marcelo Tosatti , Avi Kivity To: "David S. Ahern" Return-path: Content-Disposition: inline In-Reply-To: <481876A9.1010806@cisco.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org On Wed, Apr 30, 2008 at 07:39:53AM -0600, David S. Ahern wrote: > Avi Kivity wrote: > > David S. Ahern wrote: > >> Another tidbit for you guys as I make my way through various > >> permutations: > >> I installed the RHEL3 hugemem kernel and the guest behavior is *much* > >> better. > >> System time still has some regular hiccups that are higher than xen > >> and esx > >> (e.g., 1 minute samples out of 5 show system time between 10 and 15%), > >> but > >> overall guest behavior is good with the hugemem kernel. > >> > >> > > > > Wait, the amount of info here is overwhelming. Let's stick with the > > current kernel (32-bit, HIGHMEM4G, right?) > > > > Did you get any traces with bypass_guest_pf=0? That may show more info. > > > > My preference is to stick with the "standard", 32-bit RHEL3 kernel in the guest. > My point in the last email was that the hugemem kernel shows a remarkable > difference (it uses 3-levels of page tables right?). I was hoping that would > ring a bell with someone. IIRC, the RHEL-3 hugemem kernel is using the 4g/4g split patches which give userspace and kernelspace their own independant pagetables http://lwn.net/Articles/39925/ http://lwn.net/Articles/39283/ Dan. -- |: Red Hat, Engineering, Boston -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone