From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56877) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aO81b-0000Ej-Rr for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:07:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aO81W-0001Jf-Qb for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:07:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36736) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aO81W-0001JV-Kz for qemu-devel@nongnu.org; Tue, 26 Jan 2016 13:07:26 -0500 References: <56A7A1A8.4060704@windriver.com> <56A7A3C7.6090006@redhat.com> <56A7AB12.8060303@windriver.com> <56A7AD8C.50606@redhat.com> <56A7B1AE.2010902@windriver.com> From: Paolo Bonzini Message-ID: <56A7B5D5.70003@redhat.com> Date: Tue, 26 Jan 2016 19:07:17 +0100 MIME-Version: 1.0 In-Reply-To: <56A7B1AE.2010902@windriver.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] high outage times for qemu virtio network links during live migration, trying to debug List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Chris Friesen , libvir-list@redhat.com, qemu-devel@nongnu.org On 26/01/2016 18:49, Chris Friesen wrote: >> >> That doesn't exclude a bug somewhere in net/ code. It doesn't pinpoin= t >> it to QEMU or vhost-net. >> >> In any case, what I would do is to use tracing at all levels (guest >> kernel, QEMU, host kernel) for packet rx and tx, and find out at which >> layer the hiccup appears. >=20 > Is there a straightforward way to trace packet processing in qemu > (preferably with millisecond-accurate timestamps)? You can use tracing (docs/tracing.txt). There are two possibilities: 1) use existing low-level virtio tracepoints: virtqueue_fill (end of tx and rx operation) and virtqueue_pop (beginning of tx operation). 2) add tracepoints to hw/net/virtio-net.c (virtio_net_flush_tx, virtio_net_tx_complete, virtio_net_receive) or net/tap.c (tap_receive, tap_receive_iov, tap_send). Paolo