From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH v2 net-next] pkt_sched: fq: Fair Queue packet scheduler Date: Tue, 03 Sep 2013 22:59:36 -0700 Message-ID: <1378274376.7360.82.camel@edumazet-glaptop> References: <1377816595.8277.54.camel@edumazet-glaptop> <5226C4A0.6040709@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , netdev , Yuchung Cheng , Neal Cardwell , "Michael S. Tsirkin" To: Jason Wang Return-path: Received: from mail-pb0-f53.google.com ([209.85.160.53]:61165 "EHLO mail-pb0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756079Ab3IDF7i (ORCPT ); Wed, 4 Sep 2013 01:59:38 -0400 Received: by mail-pb0-f53.google.com with SMTP id up15so6938651pbc.40 for ; Tue, 03 Sep 2013 22:59:38 -0700 (PDT) In-Reply-To: <5226C4A0.6040709@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2013-09-04 at 13:26 +0800, Jason Wang wrote: > I see both degradation and jitter when using fq with virtio-net. Guest > to guest performance drops from 8Gb/s to 3Gb/s-7Gb/s. Guest to local > host drops from 8Gb/s to 4Gb/s-6Gb/s. Guest to external host with ixgbe > drops from 9Gb/s to 7Gb/s > > I didn't meet the issue when using sfq or disabling pacing. > > So it looks like it was caused by the inaccuracy and jitter of the > pacing estimation in a virt guest? Well, using virtio-net means you use FQ without pacing. Make sure you do not have reorders because of a bug in queue selection. TCP stack has the ooo_okay thing, I do not think a VM can get it. nstat >/dev/null ; ; nstat And tcpdump would certainly help ;)