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    SubjectRe: [Bug 350] New: i386 context switch very slow compared to 2.4 due to wrmsr (performance)

    Ok Jamie,
    since you've been interested in the past, I thought I'd ask you to test
    the current context switch stuff. Andi cleaned up some FPU reload stuff
    (and I fixed a bug in it, tssk tssk Andi - you'd obviously not actually
    timed your cleanups), and I just committed and pushed out my "cache the
    value of SYSENTER_CS in the TSS" patch.

    It won't bring context switching back to where it _could_ be, but it
    should be noticeably better. My pipe bandwidth is up from under 600MB/s
    to about ~700MB/s according to lmbench.

    Your SYSENTER_ESP hack would probably get back the rest, but I haven't
    seen any patches for it, hint hint.

    In the meantime, we're almost back to where we were _and_ we support
    sysenter (ie my system calls are down by almost a factor of four). So
    we're doing pretty well.

    Linus

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