From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Hajnoczi Subject: Re: FAQ on linux-kvm.org has broken link Date: Tue, 27 Aug 2013 09:31:04 +0200 Message-ID: <20130827073104.GA24247@stefanha-thinkpad.redhat.com> References: <20130730011852.GC27878@belle.intranet.vanheusden.com> <20130730122546.GA7239@stefanha-thinkpad.redhat.com> <20130730204514.GA9179@belle.intranet.vanheusden.com> <20130731084624.GA20915@stefanha-thinkpad.muc.redhat.com> <20130802113753.GA8801@belle.intranet.vanheusden.com> <20130802180657.GB8801@belle.intranet.vanheusden.com> <20130805113154.GD14592@stefanha-thinkpad.muc.redhat.com> <20130826195037.GA18231@belle.intranet.vanheusden.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm To: folkert Return-path: Received: from mail-ea0-f182.google.com ([209.85.215.182]:34335 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752055Ab3H0HbH (ORCPT ); Tue, 27 Aug 2013 03:31:07 -0400 Received: by mail-ea0-f182.google.com with SMTP id o10so2080072eaj.13 for ; Tue, 27 Aug 2013 00:31:06 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20130826195037.GA18231@belle.intranet.vanheusden.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Aug 26, 2013 at 09:50:38PM +0200, folkert wrote: > > 2. Get the system into the bad state and then do some deeper. Start > > with outgoing ping, instrument guest driver and host vhost_net > > functions to see what the drivers are doing, inspect the transmit > > vring, etc. Okay, it's time to understand what is going on at the virtio-net level. You can check whether the host is being notified of packets ready to be transmitted: (host)$ sudo perf probe --module vhost_net handle_tx (host)$ sudo perf record --pid 24306 -e probe:handle_tx -R [...attempt to transmit packets inside guest...] ^C (host)$ sudo perf script vhost-24305 24306 [000] 101120.817103: probe:handle_tx: (ffffffffa06fd6b0) Here the qemu-kvm process was pid 24305 and the vhost kernel thread was 24306 (you can find out the correct pid to use using ps aux). If your host is only running the guest under test you can drop the pid argument and replace it with -a. If you see handle_tx probes firing on the host then the issue may be with the vring or tap device. If you do not see handle_tx probes firing on the host, then the problem may be inside the guest. Stefan