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From: =?utf-8?Q?Llu=C3=ADs_Vilanova?= <vilanova@ac.upc.edu>
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Date: Tue, 26 Sep 2017 19:49:26 +0300
In-Reply-To: <20170925194202.GA19618@flamenco> (Emilio G. Cota's message of
	"Mon, 25 Sep 2017 15:42:02 -0400")
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Subject: Re: [Qemu-devel] [PATCH v6 01/22] instrument: Add documentation
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To: "Emilio G. Cota" <cota@braap.org>
Cc: Peter Maydell <peter.maydell@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Stefan Hajnoczi <stefanha@redhat.com>, Markus Armbruster <armbru@redhat.com>

Emilio G Cota writes:

> On Mon, Sep 25, 2017 at 21:03:39 +0300, Llu=C3=ADs Vilanova wrote:
>> I know it's not exactly the same we're discussing, but the plot in [1] c=
ompares
>> a few different ways to trace memory accesses on SPEC benchmarks:
>>=20
>> * First bar is using a Intel's tool called PIN [2].
>> * Second is calling into an instrumentation function on every executed m=
emory
>> access in QEMU.
>> * Third is embedding the hot path of writing the memory access info to a=
n array
>> into the TCG opcode stream (more or less equivalent to supporting filter=
ing;
>> when the array is full, a user's callback is called - cold path -)
>> * Fourth bar can be ignored.
>>=20
>> This was working on a much older version of instrumentation for QEMU, bu=
t I can
>> implement something that does the first use-case point above and some fi=
ltering
>> example (second use-case point) to see what's the performance difference.
>>=20
>> [1] https://filetea.me/n3wy9WwyCCZR72E9OWXHArHDw

> Interesting! Unfortunately, this URL gives me a 404.

Ok, I've uploade it somewhere else:

  https://people.gso.ac.upc.edu/vilanova/mtrace.pdf

There's also another one that simply counts the number of memory accesses, =
using
the same three approaches:

  https://people.gso.ac.upc.edu/vilanova/mcount.pdf

Cheers,
  Lluis