Re: [RFC 0/6] x86: prefetch_page() vDSO call

Peter Zijlstra
2021-02-25T10:00:50Z

On Thu, Feb 25, 2021 at 01:32:56AM -0800, Nadav Amit wrote:
> > On Feb 25, 2021, at 12:52 AM, Nadav Amit <nadav.amit@gmail.com> wrote:

> > Can you give me a reference to the “removing explicit prefetch from some
> > parts of the kernel”?

75d65a425c01 ("hlist: remove software prefetching in hlist iterators")
e66eed651fd1 ("list: remove prefetching from regular list iterators")

> Oh. I get it - you mean we remove we remove the use of explicit memory
> prefetch from the kernel code. Well, I don’t think it is really related,
> but yes, performance numbers are needed.

Right, so my main worry was that use of the prefetch instruction
actually hurt performance once the hardware prefetchers got smart
enough, this being a very similar construct (just on a different level
of the stack) should be careful not to suffer the same fate.