From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: performance tuning, problem with paravirtualized clock Date: Sun, 06 Apr 2008 17:33:23 -0500 Message-ID: <47F94FB3.7010208@codemonkey.ws> References: <47F934BD.7000502@codemonkey.ws> <47F9472E.50602@linuxbox.cz> <47F949DD.2010802@codemonkey.ws> <47F94D90.2040701@linuxbox.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net To: Nikola Ciprich Return-path: In-Reply-To: <47F94D90.2040701@linuxbox.cz> 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 Nikola Ciprich wrote: > Anthony Liguori wrote: >> You won't see a gain with tmpfs. Make sure you reserve huge pages >> first. For a 1GB guest, you'll need something like: >> >> echo 540 > /proc/sys/vm/nr_hugepages >> >> When you create a VM, you need a bit more memory than 1GB for >> per-guest overhead. That's why I reserve 540 instead of 512. You >> can probably get away with 530 really. >> >> Check that it succeeded by cat'ing /proc/meminfo. >> > Well, I tried various values now, and booting fails immediately: > Decompressing Linux... It's very likely that you won't be able to allocate enough pages to run a guest if your system has been running sufficient long and memory is highly fragmented. If you cat /proc/meminfo and HugePages_Free is much less than 540, you're not going to be able to create a 1GB guest. Unfortunately, you won't get a failure until the guest tries to use memory. The only solution is to reboot and reserve huge pages early before they get fragmented. Regards, Anthony Liguori > invalid compressed format (err=1) > > -- System halted > > > weird... > anyways I'll also give fresh kvm-65 a try now :) > ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Register now and save $200. Hurry, offer ends at 11:59 p.m., Monday, April 7! Use priority code J8TLD2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone