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Date: Mon, 25 Sep 2017 15:42:02 -0400
From: "Emilio G. Cota" <cota@braap.org>
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Subject: Re: [Qemu-devel] [PATCH v6 01/22] instrument: Add documentation
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To: Peter Maydell <peter.maydell@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Stefan Hajnoczi <stefanha@redhat.com>, Markus Armbruster <armbru@redhat.com>

On Mon, Sep 25, 2017 at 21:03:39 +0300, Lluís Vilanova wrote:
> I know it's not exactly the same we're discussing, but the plot in [1] compares
> a few different ways to trace memory accesses on SPEC benchmarks:
> 
> * First bar is using a Intel's tool called PIN [2].
> * Second is calling into an instrumentation function on every executed memory
>   access in QEMU.
> * Third is embedding the hot path of writing the memory access info to an array
>   into the TCG opcode stream (more or less equivalent to supporting filtering;
>   when the array is full, a user's callback is called - cold path -)
> * Fourth bar can be ignored.
> 
> This was working on a much older version of instrumentation for QEMU, but I can
> implement something that does the first use-case point above and some filtering
> example (second use-case point) to see what's the performance difference.
> 
> [1] https://filetea.me/n3wy9WwyCCZR72E9OWXHArHDw

Interesting! Unfortunately, this URL gives me a 404.

		E.