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    SubjectRe: [patch] procfs/procps threading performance speedup, 2.5.62
    On Thu, 2003-02-20 at 12:23, Ingo Molnar wrote:

    > architecture-wise there is a difference, and i'd be
    > the last one arguing against a tree-based approach to
    > thread groups. It's much easier to find threads belonging
    > to a single 'process' via /proc this way - although no
    > functionality in procps has or requires such a feature currently.

    Nope, the /proc/123/threads/246/stat approach is required.
    Without this, procps is forced to read _all_ tasks to
    group threads together. This is slow, prone to race conditions,
    more vulnerable to kernel bugs, and a memory hog.

    FYI, thread grouping is required even if whole-process
    information is available. Many "ps" output formats need
    grouping, and it is desirable for many more.

    I might as well mention that whole-process information
    includes the four fault counters and some indication
    that wchan data is multi-valued (a '*' must be displayed
    in that case). There may be more I haven't spotted yet.

    Note that the recent /proc/*/wchan addition was botched.
    Caching is prevented due to race conditions. This could
    be fixed by changing the file format to contain:
    number, function name
    with optional:
    function address, file name, module name
    (next time, discuss such changes with an experienced
    procps developer first)

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