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List:       netbsd-tech-kern
Subject:    Re: hf/sf [Was Re: CVS commit: pkgsrc/misc/raspberrypi-userland]
From:       Ignatios Souvatzis <is () netbsd ! org>
Date:       2013-11-13 21:48:01
Message-ID: 20131113214801.GC28325 () beverly ! kleinbus ! org
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Hi,

On Tue, Nov 12, 2013 at 07:47:20PM +0000, Michael van Elst wrote:
> matt@3am-software.com (Matt Thomas) writes:
> 
> 
> >On Nov 11, 2013, at 10:08 PM, Michael van Elst <mlelstv@serpens.de> wrote:
> 
> >> The "slowdown" is already enormous due to lack of floating point
> >> hardware. That's why emulating the FP hardware is a very common
> >> way to handle this situation, just look at the other platforms.
> 
> >The exception handling is much costlier than doing a softfloat call.
> 
> You missed the second paragraph.
> 
> >It’s also adding kernel bloat.
> 
> Indeed, a little bit of kernel bloat compared to a dozen userlands
> and a dozen package repositories that require building and testing.

Yes - I didn't measure current arms in that respect, but I did try
to add the M68060 missing FP instruction emulation package to libm
and compare to the kernel trap version a couple of years ago.

The kernel trap version turned out to be faster - I guessed because
of less (physically indexed) cache trashing.

	-is
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