kern/46897: procfs uses too small a buffer for /proc/cpuinfo (or, I have too many cores)

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

>Number:         46897
>Category:       kern
>Synopsis:       procfs uses too small a buffer for /proc/cpuinfo (or, I have 
>too many cores)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Sep 03 21:20:00 +0000 2012
>Originator:     Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
>Release:        NetBSD 6.99.10
>Organization:
>Environment:
Architecture: amd64
Machine: amd64
>Description:

        I mounted procfs on a system with 24 cores (well, 24 threads --
        two CPUs, six cores per CPU, two threads per core).  I tried to
        see what /proc/cpuinfo would say about them, only to find:

                # cat /proc/cpuinfo
                cat: /proc/cpuinfo: No space left on device

        Evidently procfs_docpuinfo allocates an 8 KB buffer for the
        whole content of /proc/cpuinfo.  Estimating from the output of
        `cpuctl identify 0', this buffer would need to be expanded by a
        factor of three to fit all my cores.

>How-To-Repeat:

        On a system with too many cores and procfs, run

                cat /proc/cpuinfo

>Fix:

        Yes, please!  Perhaps multiply the buffer size by the number of
        cores?