Messages in this thread | | | Date | Wed, 17 Sep 2003 15:19:12 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH] Athlon/Opteron Prefetch Fix for 2.6.0test5 + numbers |
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Andrew Morton wrote:
>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". >
Right. It obviously can't be done using the current system.
> >> 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. > > >
OK. I just liked this patch because apparently it fixes userspace as well. Disabling prefetch for the kernel doesn't.
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