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    SubjectRe: More latency regressions with 2.6.11-rc4-RT-V0.7.39-02
    Lee Revell wrote:
    > On Thu, 2005-02-24 at 10:27 +1100, Nick Piggin wrote:

    >>If you are using i386 with 2-level page tables (no highmem), then
    >>the behaviour should be more or less identical. Odd.
    >
    >
    > IIRC last time I really tested this a few months ago, the worst case
    > latency on that machine was about 150us. Currently its 422us from the
    > same clear_page_range code path.
    >
    > On my Athlon XP the clear_page_range latency is not showing up at all,
    > and the worst delay so far is only 35us, most of which is the timer
    > interrupt IOW that machine is showing the best achievable latency (with
    > PREEMPT_DESKTOP). The machine seeing 422 us latencies in
    > clear_page_range is a 600Mhz C3, which is known to be a FSB limited
    > architecture.
    >

    Well it should be pretty trivial to add a break in there.
    I don't think it can get into 2.6.11 at this point though,
    so we'll revisit this for 2.6.12 if the clear_page_range
    optimisations don't get anywhere.

    Nick


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