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    SubjectRe: [benchmark] 2.4.0-test6-pre1 PAE vs non-PAE
    Hi Ingo!

    On Thu, 3 Aug 2000, Ingo Molnar wrote:
    > the 3% performance drop

    that is 6, not 3. 129.6/136.5 = 0.94945054945054945054 ~ 0.94 (ok, 0.95
    but no way it is 0.97 :)

    > is mainly due to two values, 'Pipe-based Context Switching',
    >'Process Creation', and 'Execl Throughput'.

    that is 3, not 2.

    the rest of your mail makes perfect sense, thank you.

    > The fork() and
    > exec() result is understandably worse with PAE, because the 'density' of
    > page-tables is half of that of non-PAE page-tables (ie. twice as much has
    > to be copied), plus there are 3 user-space root page tables instead of the
    > 1. (which have to be zeroed, so this shows up big time.)
    >
    > Another performance problem is likely the amount of LOCK-ed instructions
    > done within the PAE include-files - some of that is unnecessery as David
    > S. Miller noticed.
    >
    > otherwise the PAE kernels show no performance drop in 'typical' user-space
    > stuff. But yes, you dont want to use it on a box with less than 4GB RAM.

    Regards,
    Tigran


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