From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: performance with guests running 2.4 kernels (specifically RHEL3) Date: Wed, 16 Apr 2008 11:46:41 +0300 Message-ID: <4805BCF1.6040605@qumranet.com> References: <48054518.3000104@cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: "David S. Ahern" Return-path: In-Reply-To: <48054518.3000104@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 David S. Ahern wrote: > I have been looking at RHEL3 based guests lately, and to say the least the > performance is horrible. Rather than write a long tome on what I've done and > observed, I'd like to find out if anyone has some insights or known problem > areas running 2.4 guests. The short of it is that % system time spikes from time > to time (e.g., on exec of a new process such as running /bin/true). > > I do not see the problem running RHEL3 on ESX, and an equivalent VM running > RHEL4 runs fine. That suggests that the 2.4 kernel is doing something in a way > that is not handled efficiently by kvm. > > Can someone shed some light on it? > It's not something that I test regularly. If you're running a 32-bit kernel, I'd suspect kmap(), or perhaps false positives from the fork detector. kvmtrace will probably give enough info to tell exactly what's going on; 'kvmstat -1' while the badness is happening may also help. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- 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