From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: High latency with VirtIO NIC Date: Thu, 24 Mar 2011 16:08:04 +0200 Message-ID: <4D8B5044.1050303@redhat.com> References: <750D7880952B4EEF856255153646029D@gmail.com> <4D8B1B4F.5070305@redhat.com> <76F180B5B89249CDA99A9521558BAF11@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Xupeng Yun Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42153 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753184Ab1CXOIJ (ORCPT ); Thu, 24 Mar 2011 10:08:09 -0400 In-Reply-To: <76F180B5B89249CDA99A9521558BAF11@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On 03/24/2011 03:45 PM, Xupeng Yun wrote: > On Thursday, March 24, 2011 at 6:22 PM, Avi Kivity wrote: > Try vhost-net, that should have much better latencies. > > Indeed, the latency is much better after switching to vhost-net, it drops from 3+ms to ~1.5ms on average > when there is no network load on the KVM guest, but the latencies become bad again when there is > heavy network load on the guest(~70Mbps RX and ~25Mbps TX). > > --------------------------- ping KVM guest (app211) from the host --------------------------- > 64 bytes from app211 (192.168.1.211): icmp_seq=3582 ttl=64 time=3.08 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3583 ttl=64 time=1.10 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3584 ttl=64 time=1.03 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3585 ttl=64 time=3.55 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3586 ttl=64 time=1.29 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3587 ttl=64 time=0.710 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3588 ttl=64 time=64.4 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3589 ttl=64 time=0.271 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3590 ttl=64 time=0.563 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3591 ttl=64 time=1.66 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3592 ttl=64 time=0.939 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3593 ttl=64 time=0.819 ms > 64 bytes from app211 (192.168.1.211): icmp_seq=3594 ttl=64 time=16.5 ms > > --------------------------- ping KVM guest (app211) from the host --------------------------- > > any idea? > Isn't it normal? With heavy load, packets start to queue. -- error compiling committee.c: too many arguments to function