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[Qemu-devel] Re: [PATCH 3/5] trace: Add LTTng Userspace Tracer backend
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH 3/5] trace: Add LTTng Userspace Tracer backend |
Date: |
Sun, 23 May 2010 17:50:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Stefan Hajnoczi wrote:
> This patch adds LTTng Userspace Tracer (UST) backend support. The UST
> system requires no kernel support but libust and liburcu must be
> installed.
>
> $ ./configure --trace-backend ust
> $ make
>
> Start the UST daemon:
> $ ustd &
>
> List available tracepoints and enable some:
> $ ustctl --list-markers $(pgrep qemu)
> [...]
> {PID: 5458, channel/marker: ust/paio_submit, state: 0, fmt: "acb %p
> opaque %p sector_num %lu nb_sectors %lu type %lu" 0x4b32ba}
> $ ustctl --enable-marker "ust/paio_submit" $(pgrep qemu)
>
> Run the trace:
> $ ustctl --create-trace $(pgrep qemu)
> $ ustctl --start-trace $(pgrep qemu)
> [...]
> $ ustctl --stop-trace $(pgrep qemu)
> $ ustctl --destroy-trace $(pgrep qemu)
>
> Trace results can be viewed using lttv-gui.
>
> More information about UST:
> http://lttng.org/ust
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> I wrote this as part of trying out UST. Although UST is promising, the
> usability is poor at the moment.
I was hoping it would be better, but I'm not really surprised.
>
> The dependencies include the lttv trace viewer which I had to build from
> source
> (and it required a makefile tweak to build). Luckily libust, liburcu, and
> ust-bin are packaged on my distro.
>
> Error messages are periodically printed by the UST code when running QEMU. I
> haven't investigated but this is may be due to signals interrupting UST's
> thread in poll().
>
> Finally, the UST header files include some userspace ported kernel
> infrastructure and pollute the namespace. I had to add some #undefs to get
> QEMU to build after including UST headers.
>
> I don't see LTTng UST as a default option at the moment. Hopefully this will
> change in the future.
Unless you already did, please report this to LTTng. I bet they will be
interested in your feedback and maybe also in the fact that they gained
another use/test case.
Jan
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- [Qemu-devel] [RFC 0/5] Tracing backends, Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] [PATCH 2/5] trace: Add simple built-in tracing backend, Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] [PATCH 4/5] trace: Trace qemu_malloc() and qemu_vmalloc(), Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] [PATCH 5/5] trace: Trace virtio-blk, multiwrite, and paio_submit, Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] [PATCH 3/5] trace: Add LTTng Userspace Tracer backend, Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] Re: [PATCH 3/5] trace: Add LTTng Userspace Tracer backend,
Jan Kiszka <=
- [Qemu-devel] [PATCH 1/5] trace: Add trace-events file for declaring trace events, Stefan Hajnoczi, 2010/05/22
- [Qemu-devel] Re: [RFC 0/5] Tracing backends, Jan Kiszka, 2010/05/23