Re: [PATCH 09/10] x86-32: use SSE for atomic64_read/set if available

[H. Peter Anvin]

On 02/18/2010 10:42 AM, Luca Barbieri wrote:
>> We already do that kind of stuff, using
>> kernel_fpu_begin()..kernel_fpu_end().  We went through some pain a bit
>> ago to clean up "private hacks" that complicated things substantially.
> 
> But that saves the whole FPU state on the first usage, and also
> triggers a fault when userspace attempts to use it again.
> Additionally it does a clts/stts every time which is slow for small
> algorithms (lke the atomic64 routines).
> 
> The first issue can be solved by using SSE and saving only the used
> registers, and the second with lazy TS flag restoring.
> 

Again, I want to see a strong use case before even *considering* making
the rules we already have any more complex.

	-hpa
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