Re: [RFC] use of /sys versus /proc

[Alexey Dobriyan]

On Fri, May 23, 2008 at 08:12:55AM -0500, Cliff Wickman wrote:
> I have a need to display TLB shootdown statistics.  (I'm working
> on a patch to implement this on a new machine at SGI.)
> 
> I had planned to display these statistics through /proc
> as in arch/ia64/sn/kernel/sn2/sn2_smp.c (/proc/sgi_sn/ptc_statistics).
> 
> However, considering the general move to reserve /proc for
> process-related things, I thought the community might prefer the
> interface to be in /sys.
> 
> But sysfs has an output buffer restriction of one page, which
> is too restrictive for statistics from very large cpu counts.
> We intend to display about 10 numbers per cpu.
> 
> Besides, the spirit of /sys according to the sysfs.txt documentation:
>     "Attributes should be ... preferably with only one value
>      per file. ... acceptable to express an array of values of the same type."
>   [it also  warns:
>     "... expressing multiple lines of data, ... is heavily frowned upon.
>      Doing these things may get you publically humiliated and your code
>      rewritten without notice."]
> 
> If I break up the statistics files per-cpu, or maybe ranges of
> cpu's, it would create a potentially large number of files in /sys.
> 
> Or, I could stick with a single file in /proc.
> 
> What would you recommend?

TLB shootdowns are in /proc/interrupts at least on x86_64.

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