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References: <5696D9FE.9060409@mentor.com> <87oabrw06k.fsf@linaro.org>
From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
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Date: Mon, 08 Feb 2016 18:34:06 +0000
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Subject: Re: [Qemu-devel] trace: timestamps, core IDs, and file creation
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To: Hollis Blanchard <hollis_blanchard@mentor.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, QEMU Developers <qemu-devel@nongnu.org>


Alex Bennée <alex.bennee@linaro.org> writes:

> Hollis Blanchard <hollis_blanchard@mentor.com> writes:
>
>> Hi Stefan, I've been starting to use qemu tracing and found it quite
>> useful. I have a couple comments about the trace events in general:
>>
> <snip>
>> Right now, the simple tracepoint backend creates a trace file even when
>> no events are active and no -trace options are present. Compounding the
>> situation, omitting "-trace file=foo" results in the directory being
>> littered with trace-NNNN files... could we create the file only when
>> tracing is activated? And maybe with a more predictable name?
>
> Yeah I've run into trouble when running "make check" with the simple
> backend enabled. I'm not sure exactly what mechanism breaks the test but
> it seems to me an invocation like:
>
>   ./x86_64-softmmu/qemu-system-x86_64 -qtest
>   unix:/tmp/qtest-9458.sock,nowait -qtest-log /dev/null -qmp
>   unix:/tmp/qtest-9458.qmp,nowait -machine accel=qtest -display none -M
>   pc -device pc-testdev
>
> Shouldn't be generating anything unless an explicit file is set.
>
> AFAICT 41fc57e44ed64cd4ab5393d83624afd897dabd4f is triggering the
> default file behaviour.
>
> I'm still digging into this.

OK ignore me, that commit breaks "make check" but not while spamming the
trace-files. That must be later in my tree.


--
Alex Bennée