From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julian Stecklina Subject: Re: Networking latency - what to expect? Date: Thu, 29 Nov 2012 17:35:51 +0100 Message-ID: <87hao8jriw.fsf@os.inf.tu-dresden.de> References: <65e3a10030795eacd577b0fac1a10bb1@de.mcbf.net> <87lidkjwho.fsf@os.inf.tu-dresden.de> Mime-Version: 1.0 Content-Type: text/plain Cc: To: David Mohr Return-path: Received: from os.inf.tu-dresden.de ([141.76.48.99]:35858 "EHLO os.inf.tu-dresden.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751013Ab2K2Qfy (ORCPT ); Thu, 29 Nov 2012 11:35:54 -0500 In-Reply-To: (David Mohr's message of "Thu, 29 Nov 2012 08:50:41 -0700") Sender: kvm-owner@vger.kernel.org List-ID: Thus spake David Mohr : > On 2012-11-29 07:48, Julian Stecklina wrote: >> Thus spake David Mohr : >> >>> * vm->vm (same host) 22k >> >> This number is in the same ballpark as what I am seeing on pretty >> much >> the same hardware. >> >> AFAICS, there is little you can do to the current virtio->virtio code >> path that would make this substantially faster. > > Thanks for the feedback. Considering that it's better than the > hardware network performance my main issue is actually the latency of > communication between VMs on different hosts: > * vm->vm (diff. hosts) 7k > > It is obvious that there is a lot more going on compared to same host > communication, but only ~30% of the performance when the network > hardware should not be slowing it down (too) much? You are probably better of using SR-IOV NICs with PCI passthrough in this case. Maybe someone can comment on whether virtual interrupt delivery and posted interrupts[1] are already usable. The first one should help in either the virtio and SR-IOV scenarios, the latter only applies to SR-IOV (and PCI passthrough in general). Julian [1] http://www.spinics.net/lists/kvm/msg82762.html