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Re: [Qemu-devel] [PATCH v4 4/9] target-ppc: improve lxvw4x implementatio


From: David Gibson
Subject: Re: [Qemu-devel] [PATCH v4 4/9] target-ppc: improve lxvw4x implementation
Date: Thu, 29 Sep 2016 13:57:29 +1000
User-agent: Mutt/1.7.0 (2016-08-17)

On Wed, Sep 28, 2016 at 08:48:54PM -0700, Richard Henderson wrote:
> On 09/28/2016 08:41 PM, Nikunj A Dadhania wrote:
> > Without patch:
> > ==============
> > [tcg_test]$ time ../qemu/ppc64le-linux-user/qemu-ppc64le  -cpu POWER9 
> > le_lxvw4x  >/dev/null
> > real        0m2.812s
> > user        0m2.792s
> > sys 0m0.020s
> > [tcg_test]$
> > 
> > With patch:
> > ===========
> > [tcg_test]$ time ../qemu/ppc64le-linux-user/qemu-ppc64le  -cpu POWER9 
> > le_lxvw4x  >/dev/null
> > real        0m2.801s
> > user        0m2.783s
> > sys 0m0.018s
> > [tcg_test]$
> > 
> > Not much perceivable difference, is there a better way to benchmark?
> 
> There should be more of a difference for softmmu, since the tlb lookup for
> the memory is more expensive.

Good point.  Oh.. also, I'd remove the prints from the benchmark for
this purpose.  The time involved in the syscalls and whatnot for the
print will just add noise to the measurement (sending to /dev/null
reduces the impact, but it's probably still significant compared to a
simple math operation).

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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