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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 19 Oct 2015 14:54:16 +0100
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Subject: Re: [Qemu-devel] What's the intended use of log.h logging?
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To: Markus Armbruster <armbru@redhat.com>
Cc: Pavel Butsykin <pbutsykin@virtuozzo.com>, QEMU Developers <qemu-devel@nongnu.org>, Luiz Capitulino <lcapitulino@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, "Denis V. Lunev" <den@openvz.org>

On 19 October 2015 at 14:17, Markus Armbruster <armbru@redhat.com> wrote:
> Peter Maydell <peter.maydell@linaro.org> writes:
>> In a lot of cases, especially with the TCG logging, not enabling
>> voluminous tracing is really important because if you turn it all
>> on then the system is way too slow (and can behave differently
>> as a result), and generates gigabytes of trace output. (-d exec
>> and -d cpu will do this, for instance.)
>
> This is at least as much an argument for use of tracing as against it.
> Tracing is a lot more flexible than log.h, and with the right backend,
> it's much more efficient, too.
>
> If the appropriate trace patterns turn out to be too hard to remember,
> we can provide canned trace patterns with names that are easy to
> remember.
>
> -d could become sugar for a suitable trace patterns.

I don't object to the use of tracing under the hood, as long as
the user-facing experience remains as good as what we have for -d
at the moment (in terms of it being always present, working the
same for everybody, easily discoverable and simple to use).

thanks
-- PMM