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SubjectRe: [patch 1/2] x86,fpu: split FPU state from task struct
On Sun, Feb 24, 2008 at 08:27:30AM +0100, Roger While wrote:
>
> On Sat, Feb 23, 2008 at 06:34:38PM -0800, Suresh Siddha wrote:
> > Split the FPU save area from the task struct. This allows easy migration
> > of FPU context, and it's generally cleaner. It also allows the following
> > two optimizations:
> >
> > 1) only allocate when the application actually uses FPU, so in the first
> > lazy FPU trap. This could save memory for non-fpu using apps. Next patch
> > does this lazy allocation.
> >
> > 2) allocate the right size for the actual cpu rather than 512 bytes
> always.
> > Patches enabling xsave/xrstor support (coming shortly) will take advantage
> > of this.
>
> > if (next_p->fpu_counter>5)
> > - prefetch(&next->i387.fxsave);
> > + prefetch(FXSAVE(next_p));
>
> Shouldn't that be prefetch(FXSAVE(next)); ?

No. 'next_p' which is the task_struct is what FXSAVE macro takes.

thanks,
suresh


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