Nick Piggin <piggin@xxxxxxxxxxxxxxx> wrote:
What is intriguing to me is the "Its only a 2% slowdown of the page
fault for every cpu other than K[78] for this single workaround. There
is no point to conditional compilation" attitude some people have.
Of course, its only 2% on a pagefault, not anywhere near 2% of kernel
performance as a whole, so maybe that is justified.
Absolutely. But it's a bit of a pain finding a config option which says
"this CPU might need the fixup".
Just repeating though, that is a seperate issue and I think Andi's patch
is needed.
It is unquestionably needed - the kernel _has_ to perform the fixup for this
CPU erratum.
But I would like to see some evidence that prefetch ever provides any
performance gain in-kernel. I spent some time fiddling a while back and
was unable to demonstrate any difference.