Re: [PATCH] Mutilated form of Andi Kleen's AMD prefetch errata patch

[Andi Kleen]

Andrew Morton <akpm@xxxxxxxx> writes:

> Looking at Andi's patch, it is also a dead box if the fault happens inside
> down_write(mmap_sem).  That should be fixed, methinks.

The only way to fix all that would be to move the instruction checks early
into the fast path.

[On a P4 the overhead is 3.7268 vs 3.6594 microseconds for a fault that 
doesn't hit as measured by lmbench2's lat_sig. This was before the latest 
changes which added more checking, so the overhead is probably bigger now]

-Andi
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