From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: kvm-27 vs 28 I/O speed Date: Fri, 06 Jul 2007 12:07:37 -0700 Message-ID: <1183748857.10287.198.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-devel Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org I've noticed that some of my tests run *MUCH* slower in kvm-28 than in 27. I'm sure that wall time is pretty wonky in the guests, but it is much slower in real-world time as well. Here's a little test to create a 32MB zeroed file with dd. Here it is from kvm-27 (this took ~5.5 seconds on my wristwatch): 33554432 bytes transferred in 0.052050 seconds (644657845 bytes/sec) 33554432 bytes transferred in 0.062933 seconds (533176451 bytes/sec) Here's the same thing from kvm-28 (~80 seconds on my wristwatch): 33554432 bytes transferred in 38.607065 seconds (869127 bytes/sec) 33554432 bytes transferred in 22.274318 seconds (1506418 bytes/sec) Same host kernel, same kvm kernel modules (from kvm-28) same guest kernel, same command-line options, same disk image. Any ideas what is going on? -- Dave ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/