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Date: Sat, 6 Oct 2018 21:42:16 -0400
From: "Emilio G. Cota" <cota@braap.org>
Message-ID: <20181007014216.GC23787@flamenco>
References: <20181005154910.3099-1-alex.bennee@linaro.org>
	<20181005154910.3099-5-alex.bennee@linaro.org>
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In-Reply-To: <20181005154910.3099-5-alex.bennee@linaro.org>
Subject: Re: [Qemu-devel] [RFC PATCH 04/21] trace: enable the exec_tb trace
 events
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To: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org, Pavel.Dovgaluk@ispras.ru, vilanova@ac.upc.edu, Paolo Bonzini <pbonzini@redhat.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Richard Henderson <rth@twiddle.net>

On Fri, Oct 05, 2018 at 16:48:53 +0100, Alex Bennée wrote:
> Our performance isn't so critical that we can't spare a simple flag
> check when we exec a TB considering everything else we check in the
> outer loop.

[I know this is just done to illustrate how function names
in plugins can bind to tracing calls, but someone might
get confused by expecting more from "exec_tb" than it
actually does.]

This flag check costs nothing because "exec_tb" is
almost never called. The way it works right now, we
need -d nochain for "exec_tb" to actually generate
an event every time a TB executes.

IMO an eventual plugin API should let plugins decide whether
to subscribe to the execution of a particular TB, when
said TB is being translated, instead of providing
an all-or-nothing switch.

Thanks,

		E.