RE: why Does Kernel Module should not do Floating Point operation?

"Manjunath_Naik" <Manjunath_Naik@xxxxxxxxxx> · Tue, 27 Jun 2006 15:28:45 +0530

What is
meant by FPU? How does it relates to kernel?

Does it is
hardware which does the floating point operation or something else?

From: Fernando
Apesteguía [mailto:fernando.apesteguia@xxxxxxxxx] 

Sent: Tuesday, June 27, 2006 2:16
PM

To: Manjunath_Naik

Cc: kernelnewbies

Subject: Re: why Does Kernel
Module should not do Floating Point operation?

Because the status of the
FPU is not saved. You can't use MMX for the same reason.

Best regards

On 6/27/06, Manjunath_Naik
< Manjunath_Naik@xxxxxxxxxx>
wrote:

Hi
all,

Why
Does Kernel Module should not do Floating Point operation? If it does what is
the problem?

Please
provide more links or articles towards the reason?

I
got the following answer from http://kerneltrap.org/node/6405 which I am not able to
understand.

   saving and restoring the FPU
state on every syscall and interrupt is just slow, so it was a design decision
not to do that. architectures with more registers than i386 even decided to
only use some of them in kernel code to avoid saving and restoring the whole
set, or they have a second set of registers just for supervisor code. as with
the FPU, code that needs the by default unsaved registers can always save them
itself.

Please
any explanation

Thanks

Manjunath
Naik

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