Messages in this thread | | | Date | Tue, 16 Sep 2003 22:08:43 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Athlon/Opteron Prefetch Fix for 2.6.0test5 + numbers |
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Nick Piggin <piggin@cyberone.com.au> 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.
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