From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Hajnoczi Subject: Re: [RFC PATCH 0/6] virtio-trace: Support virtio-trace Date: Tue, 24 Jul 2012 11:02:04 +0100 Message-ID: References: <20120724023657.6600.52706.stgit@ltc189.sdl.hitachi.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120724023657.6600.52706.stgit@ltc189.sdl.hitachi.co.jp> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Yoshihiro YUNOMAE Cc: Herbert Xu , Arnd Bergmann , Greg Kroah-Hartman , Frederic Weisbecker , Dhaval Giani , qemu-devel@nongnu.org, Borislav Petkov , linux-kernel@vger.kernel.org, "Franch Ch. Eigler" , Ingo Molnar , Mathieu Desnoyers , Steven Rostedt , Anthony Liguori , yrl.pp-manager.tt@hitachi.com, Amit Shah , virtualization@lists.linux-foundation.org, Srikar Dronamraju List-Id: virtualization@lists.linuxfoundation.org On Tue, Jul 24, 2012 at 3:36 AM, Yoshihiro YUNOMAE wrote: > The performance of each method is compared as follows: > [1] Native > - only recording trace data to ring-buffer on a guest > [2] Virtio-trace > - running a trace agent on a guest > - a reader on a host opens FIFO using cat command > [3] IVRing > - A SystemTap script in a guest records trace data to IVRing. > -- probe points are same as ftrace. > [4] Virtio-serial(normal) > - A reader(using cat) on a guest output trace data to a host using > standard output via virtio-serial. The first time I read this I thought you are adding a new virtio-trace device. But it looks like this series really add splice support to virtio-console and that yields a big performance improvement when sending trace_pipe_raw. Guest ftrace is useful and I like this. Have you thought about controlling ftrace from the host? Perhaps a command could be added to the QEMU guest agent which basically invokes trace-cmd/perf. Are you using text formatted ftrace? Stefan