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SubjectRe: [RFC PATCH 0/6] virtio-trace: Support virtio-trace
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On Tue, Jul 24, 2012 at 3:36 AM, Yoshihiro YUNOMAE
<yoshihiro.yunomae.ez@hitachi.com> 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


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