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    SubjectRe: [benchmark] 1% performance overhead of paravirt_ops on native kernels
    On Thu, Jun 04, 2009 at 08:02:14AM -0700, Linus Torvalds wrote:
    > On Thu, 4 Jun 2009, Rusty Russell wrote:
    > > >
    > > > Turn off HIGHMEM64G, please (and HIGHMEM4G too, for that matter - you
    > > > can't compare it to a no-highmem case).
    > >
    > > Thanks, your point is demonstrated below. I don't think HIGHMEM4G is
    > > unreasonable for a distro tho, so I turned that on instead.
    > Well, I agree that HIGHMEM4G is a _reasonable_ thing to turn on.
    > The thing I disagree with is that it's at all valid to then compare to
    > some all-software feature thing. HIGHMEM doesn't expand any esoteric
    > capability that some people might use - it's about regular RAM for regular
    > users.
    > And don't get me wrong - I don't like HIGHMEM. I detest the damn thing. I
    > hated having to merge it, and I still hate it. It's a stupid, ugly, and
    > very invasive config option. It's just that it's there to support a
    > stupid, ugly and very annoying fundamental hardware problem.

    I was looking forward to be able to get rid of it... unfortunately
    other 32-bit architectures are starting to use it again :(

    I guess it is not incredibly intrusive for generic mm code. A bit
    of kmap sprinkled around which is actually quite a useful delimiter
    of where pagecache is addressed via its kernel mapping.

    Do you hate more the x86 code? Maybe that can be removed?

     \ /
      Last update: 2009-06-09 11:41    [W:0.024 / U:37.820 seconds]
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