Re: [REPORT] [GSoC - TCG Continuous Benchmarking] [#2] Dissecting QEMU Into Three Main Parts

[Ahmed Karaman]

On Sat, Jul 4, 2020 at 10:45 AM Alex Bennée <alex.bennee@linaro.org> wrote:
>
>
> Aleksandar Markovic <aleksandar.qemu.devel@gmail.com> writes:
>
> > On Wednesday, July 1, 2020, Alex Bennée <alex.bennee@linaro.org> wrote:
> >
> >>
> >> Ahmed Karaman <ahmedkhaledkaraman@gmail.com> writes:
> >>
> >> > On Mon, Jun 29, 2020 at 6:03 PM Alex Bennée <alex.bennee@linaro.org>
> >> wrote:
> >> >>
> >> >> Assuming your test case is constant execution (i.e. runs the same each
> >> >> time) you could run in through a plugins build to extract the number of
> >> >> guest instructions, e.g.:
> >> >>
> >> >>   ./aarch64-linux-user/qemu-aarch64 -plugin tests/plugin/libinsn.so -d
> >> plugin ./tests/tcg/aarch64-linux-user/sha1
> >> >>   SHA1=15dd99a1991e0b3826fede3deffc1feba42278e6
> >> >>   insns: 158603512
> >> >>
> >> >> --
> >> >> Alex Bennée
> >> >
> >> > Hi Mr. Alex,
> >> > I've created a plugins build as you've said using "--enable-plugins"
> >> option.
> >> > I've searched for "libinsn.so" plugin that you've mentioned in your
> >> > command but it isn't in that path.
> >>
> >> make plugins
> >>
> >> and you should find them in tests/plugins/
> >>
> >>
> > Hi, both Alex and Ahmed,
> >
> > Ahmed showed me tonight the first results with number of guest
> > instructions. It was almost eye-opening to me. The thing is, by now, I had
> > only vague picture that, on average, "many" host instructions are generated
> > per one guest instruction. Now, I could see exact ratio for each target,
> > for a particular example.
> >
> > A question for Alex:
> >
> > - What would be the application of this new info? (Except that one has nice
> > feeling, like I do, of knowing the exact ratio host/guest instruction for a
> > particular scenario.)
>
> Well I think the total number of guest instructions is important because
> some architectures are more efficient than others and this will an
> impact on the total executed instructions.
>
> > I just have a feeling there is more significance of this new data that I
> > currently see. Could it be that it can be used in analysis of performance?
> > Or measuring quality of emulation (TCG operation)? But how exactly? What
> > conclusion could potentially be derived from knowing number of guest
> > instructions?
>
> Knowing the ratio (especially as it changes between workloads) means you
> can better pin point where the inefficiencies lie. You don't want to
> spend your time chasing down an inefficiency that is down to the guest
> compiler ;-)
>
> >
> > Sorry for a "stupid" question.
> >
> > Aleksandar
> >
> >
> >
> >
> >> >
> >> > Are there any other options that I should configure my build with?
> >> > Thanks in advance.
> >> >
> >> > Regards,
> >> > Ahmed Karaman
> >>
> >>
> >> --
> >> Alex Bennée
> >>
>
>
> --
> Alex Bennée

Thanks Mr. Alex for your help!

Regards,
Ahmed Karaman