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    SubjectRe: [ANNOUNCE] Native POSIX Thread Library 0.1

    On Mon, 23 Sep 2002, Peter Waechtler wrote:

    > Getting into kernel is not the same as a context switch. Return EAGAIN
    > or EWOULDBLOCK is definetly _not_ causing a context switch.

    this is a common misunderstanding. When switching from thread to thread in
    the 1:1 model, most of the cost comes from entering/exiting the kernel. So
    *once* we are in the kernel the cheapest way is not to piggyback to
    userspace to do some userspace context-switch - but to do it right in the
    kernel.

    in the kernel we can do much higher quality scheduling decisions than in
    userspace. SMP affinity, various statistics are right available in
    kernel-space - userspace does not have any of that. Not to talk about
    preemption.

    Ingo

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