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Re: Benchmark performance

To: Atsushi Nemoto <nemoto@toshiba-tops.co.jp>
Subject: Re: Benchmark performance
From: Carsten Langgaard <carstenl@mips.com>
Date: Thu, 16 Aug 2001 09:43:23 +0200
Cc: wgowcher@yahoo.com, linux-mips@oss.sgi.com
References: <20010809215522.A1958@lucon.org> <20010813173446.61234.qmail@web11901.mail.yahoo.com> <20010816125652N.nemoto@toshiba-tops.co.jp>
Sender: owner-linux-mips@oss.sgi.com
Atsushi Nemoto wrote:

> >>>>> On Mon, 13 Aug 2001 10:34:46 -0700 (PDT), Wayne Gowcher 
> >>>>> <wgowcher@yahoo.com> said:
> wgowcher> a 23 % reduction in the Floating Point Index benchmark
>
> Current CVS kernel uses FPU emulator unconditionally.  If one floating
> point intruction causes a 'Unimplemented' exception (denormalized
> result, etc.) following floating point instructions are also handle by
> FPU emulator (not only the instruction which raise the exception).

You got a point here, no need to emulate following floating point instructions, 
if one got
a real FPU.
But I think the check in the FP emulator should be a check if we got a real 
FPU, instead of
a counter.
We already has a flag for that in mips_cpu.options.
The check could be something like:

    if (mips_cpu.options & MIPS_CPU_FPU)
        break;



>
> I do not know this is really desired behavior, but here is a patch to
> change this.  If Unimplemented exception had been occured during the
> benchmark, aplying this patch may result better performance.
>
> ---
> Atsushi Nemoto
>
>   ------------------------------------------------------------------------
>                     Name: fpu_emu.patch
>    fpu_emu.patch    Type: Plain Text (Text/Plain)
>                 Encoding: 7bit

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