Messages in this thread | | | Date | Fri, 23 May 2008 15:08:42 -0500 | From | Robin Holt <> | Subject | Re: [RFC] use of /sys versus /proc |
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On Sat, May 24, 2008 at 12:47:39AM +0400, Alexey Dobriyan wrote: > 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.
This is a different engine for our UV platform. Due to the large number of nodes with many cpus that may need to be invalidated, we have a special piece of hardware that assists in broadcasts. Cliff's upcoming patch will introduce that. He has written the driver with some built-in statistics about the use of that hardware.
Thanks, Robin
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