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Re: [Qemu-devel] Static tracepoint control via trace-event
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] Static tracepoint control via trace-event |
Date: |
Tue, 19 Oct 2010 14:36:59 +0100 |
User-agent: |
Mutt/1.4.1i |
On Tue, Oct 19, 2010 at 03:08:08PM +0200, Jan Kiszka wrote:
> Hi Stefan,
>
> just had a closer look at qemu's new tracing framework. Looks cool,
> though it leaves a bit room for improvements. ;)
>
> One quirk I stumbled over quickly was the "disable" tag in trace-events.
> It confused me first as qemu starts without any tracepoint enabled by
> default and I thought I had to hack the file. Then I read the doc and
> wondered which exiting or future backend would come without sufficiently
> fast dynamic tracepoint control. Do you have any in mind?
>
> Instead of making it a compile-time switch (except for simpletrace), I
> would vote for declaring the simpletrace usage as the only one: disable
> sets the default state of the dynamic tracepoint. That way we could use
> trace-events to define a useful set of standard, moderate-impact
> tracepoints that shall be on. Others will still be available once a
> backend is configured, but remain off until enabled during runtime.
> Anything else looks like overkill to me.
FYI with the DTrace/SystemTAP backend I posted yesterday, the 'disable'
keyword is effectively completely ignored. All tracepoints are disabled
when QEMU is running normally. Only when a end user runs a dtrace script
that references a QEMU tracepoint, is that specific tracepoint enabled.
Regards,
Daniel
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- [Qemu-devel] Static tracepoint control via trace-event, Jan Kiszka, 2010/10/19
- Re: [Qemu-devel] Static tracepoint control via trace-event,
Daniel P. Berrange <=
- Re: [Qemu-devel] Static tracepoint control via trace-event, Stefan Hajnoczi, 2010/10/19
- Re: [Qemu-devel] Static tracepoint control via trace-event, Jan Kiszka, 2010/10/19
- Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Richard W.M. Jones, 2010/10/19
- [Qemu-devel] Re: Tracing block devices, Jan Kiszka, 2010/10/19
- Re: Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Stefan Hajnoczi, 2010/10/19
- Re: Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Christoph Hellwig, 2010/10/21
- Re: Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Richard W.M. Jones, 2010/10/21
- Re: Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Stefan Hajnoczi, 2010/10/21
- Re: Tracing block devices (was: Re: [Qemu-devel] Static tracepoint control via trace-event), Daniel P. Berrange, 2010/10/21