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    SubjectRe: X15 alpha release: as fast as TUX but in user space (fwd)
    Ingo Oeser writes:
    > On Sun, Apr 29, 2001 at 12:48:06PM -0600, Richard Gooch wrote:
    > > Ingo Oeser writes:
    > > > There we have 10x faster memmove/memcpy/bzero for 1K blocks
    > > > granularity (== alignment is 1K and size is multiple of 1K), that
    > > > is done by the memory controller.
    > > This sounds different to me. Using the memory controller is (should
    > > be!) a privileged operation, thus it requires a system call. This is
    > > quite different from code in a magic page, which is excuted entirely
    > > in user-space. The point of the magic page is to avoid the syscall
    > > overhead.
    >
    > Yes, but we currently have more than 10K cycles for doing
    > memset of a page. If we do an syscall, we have around 600-900
    > (don't know exactly), which is still less.
    >
    > The point is: The code in that "magic page" that considers the
    > tradeoff is KERNEL code, which is designed to care about such
    > trade-offs for that machine.

    Um, yes. I don't disagree with that. I'm just saying the two issues
    are conceptually separate, and should be considered independently.

    > Glibc never knows this stuff and shouldn't, because it is already
    > bloated.

    True, true and true.

    Regards,

    Richard....
    Permanent: rgooch@atnf.csiro.au
    Current: rgooch@ras.ucalgary.ca
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