floating points in kernel space

[julie Sullivan]

> I think the issue is the kernel is extremely concerned with the
> efficiency of the syscall path.
>
> Very legitimately some benchmarks just measure that one path to see
> how many thousands of syscalls per second can be made.
>
> To accelerate that path as much as possible, the linux kenel chooses
> not to incur the overhead of preserving the FP registers on every
> syscall.
>
> So kernel code that uses FP must first ensure any registers it uses
> are preserved.  I don't recall ever writing any FP kernel code, so I
> don't know what facilities are available to do that.
>
> Greg
>

Greg

I had a vague idea about overhead being incurred due to the mode switch, but

your clear explanation makes it a lot easier to understand _where_ this
happens.
It's very helpful, thank you for your response.

Julie
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