performance: memcpy vs. __copy_tofrom_user

Benjamin Herrenschmidt benh at kernel.crashing.org
Tue Oct 14 07:50:27 EST 2008


> It doesn't need to be done in non-preemptible sections, if you have a
> separate per-thread save area for kernel fp/altivec use (and appropriate
> flags so an FP unavailable handler knows which regs to restore), and you
> can avoid using it in a preempting context.

Yuck.

Ben.





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