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    DateWed, 20 Dec 2006 00:40:57 -0500
    From"Albert Cahalan" <>
    SubjectRe: [PATCH] procfs: export context switch counts in /proc/*/stat
    David Wragg writes:
    > Benjamin LaHaise <bcrl@kvack.org> writes:
    >> On Mon, Dec 18, 2006 at 11:50:08PM +0000, David Wragg wrote:
    
    >>> This patch (against 2.6.19/2.6.19.1) adds the four context
    >>> switch values (voluntary context switches, involuntary
    >>> context switches, and the same values accumulated from
    >>> terminated child processes) to the end of /proc/*/stat,
    >>> similarly to min_flt, maj_flt and the time used values.
    
    Hmmm, OK, do people have a use for these values?
    
    >> Please put these into new files, as the stat files in /proc are
    >> horribly overloaded and have always been somewhat problematic
    >> when it comes to changing how things are reported due to internal
    >> changes to the kernel.  Cheers,
    
    No thanks. Yours truly, the maintainer of "ps", "top", "vmstat", etc.
    
    > The delay accounting value was added to the end of /proc/pid/stat back
    > in July without discussion, so I assumed this approach was still
    > considered satisfactory.
    
    /proc/*/stat is the very best place in /proc for any per-process
    data that will be commonly needed. Unlike /proc/*/status, few
    people are tempted to screw with the formatting and/or spelling.
    Unlike the /sys crap, it doesn't take 3 syscalls PER VALUE to
    get at the data.
    The things to ask are of course: will this really be used, and
    does it really belong in /proc at all?
    
    > Putting just these four values into a new file would seem a little
    > odd, since they have a lot in common with the other getrusage values
    > that are already in /proc/pid/stat.  One possibility is to add
    > /proc/pid/rusage, mirroring the full struct rusage in text form, since
    > struct rusage is already part of the kernel ABI (though Linux doesn't
    > fill in half of the values).
    
    Since we already have a struct defined and all...
    
    sys_get_rusage(int pid)
    
    > Or perhaps it makes sense to reorganize all the values from
    > /proc/pid/stat and its siblings into a sysfs-like one-value-per-file
    > structure, though that might introduce atomicity and efficiency issues
    > (calculating some of the values involves iterating over the threads in
    > the process; with everything in one file, these loops are folded
    > together).
    
    Yeah, big time. Things are quite bad in /proc, but /sys is a joke.
    -
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