> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Adrian Schmitz > Sent: Thursday, December 11, 2008 12:33 PM > To: [email protected] > Subject: Slow virtio networking > > Can anyone provide any pointers as to what might cause virtio > networking > to be slow (~55Mb/s)? Here's what I've tried so far: > > Guests tried: > > Windows Server 2003 x32 SP2 UP guest w/ Windows guest drivers ver 3 > > Windows Server 2003 x64 SP2 SMP guest w/ Windows guest drivers ver 3 > > > On the host: > > On all the hosts I'm using CentOS 5.2 x64. Two of the three physical > servers I've tried are dual Intel Xeon E5430s (Dell 2950s). The third > server is a Dual Opteron 2350 (Dell R805). All the servers are brand > new > and have almost no load currently. > > I've tried using KVM-79 built against the stock 2.6.18 kernel, KVM-79 > built against a custom 2.6.27.8 kernel, and git (on 12/10/08) built > against 2.6.27.8. > > In all cases, I've made sure to copy the if_tun.h and virtio*.h from my > current kernel includes into the kernel/include/linux directory in my > kvm-79 or kvm-userspace source tree before building, since I've heard > this is necessary to enable GSO support, although I've also been told > that lacking GSO shouldn't make it quite as slow as it is. > > In all cases, when I test throughput from the guest using virtio to the > host's br0 (the bridge the guest is joined to), I get somewhere between > 55Mb/s and 150Mb/s. This is even less than I get with the rtl8139 and > e1000 emulation (between 200 and 350 Mb/s). > > Everything else with this host and guest works great. Pings from guest > to host are perfect (on the intel servers, not on the amd server but > that's another issue I believe). Is there something I could be doing > wrong during my host kernel config, or during my kvm build, etc that > could cause virtio to work, but so slowly? Any ideas are greatly > appreciated. > > > -Adrian
I setup virtio networking for a linux (Ubuntu Hardy) guest on one of the above servers and I get 1.12Gb/s. So, it seems I'm only having the aforementioned problem on Windows guests. Originally I was using the guest drivers version 2, but I was getting frequent BSOD crashes on my guests. Dor Laor provided me version 3 drivers which solved my BSOD issues. Is it possible I'm misconfiguring the guest drivers somehow? The only other difference between the guests is that acpi is disabled on the linux guest (the one that works) and it is enabled on the two windows guests (The ones with slow virtio). I can't disable acpi on one of them because it is windows x64, and can't disable it on the other server until off-hours. Any opinions on whether this is more likely related to the windows guest drivers or to the acpi being enable/disabled? -Adrian -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
