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    SubjectRe: What /proc should contain [was: /proc/driver/microcode]
    Jamie Lokier wrote:
    > Would a binary file in each /proc/PID directory containing just the right
    > information for /proc be ok?

    You mean for ps or top ? Why stop there ? If all you want is a highly
    efficient interface for top, create a single binary interface that
    just spits out those bits of information in fixed-size binary records,
    for all processes at once. For kernel version independence, you can
    create a map for the binary data, a bit like ksyms.


    $ cat /proc/
    #field offset size
    pid 0 2
    pri 2 2
    uid 4 4

    Then read and lseek on /proc/psbin to extract all the data.

    If necessary, add filtering capabilities, e.g. turn "offset" into an
    ID number and let the user write a filter that picks fields based on
    their ID. You can further optimize this in the kernel into a list of
    parameters to memcpy, handling adjacent fields in a single copy. Now
    this really screams ;-)

    It's easy to optimize for a small number of well-defined and reasonably
    stable cases. You still have the more general and less efficient text
    files for more special uses, where performance is less critical (e.g.
    things like fuser). Also, the text files have better granularity for
    permissions than such an all-or-nothing /proc/psbin.

    - Werner

    / Werner Almesberger, ICA, EPFL, CH /

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