Sysctl as a Service, or: making sysctl(3) more friendly for monitoring systems

[Peter Jeremy]

On 2016-Dec-11 16:42:38 -0330, Jonathan Anderson <jonathan at FreeBSD.org> wrote:
>I, for one, agree, and at the risk of being slightly provocative, I 
>think it could be taken even further. :) I'd love to be able to retrieve 
>a sysctl entry or subtree as an nvlist_t. Rather than doing lots of 
>system calls to enumerate clearly-related sysctl values, it would be 
>very cool to do one system call and then inspect the resulting data 
>structure in memory. We already use libnv in a number of places, and it 
>seems like it could be a natural mapping from the sysctl hierarchy.

This is just pushing the work from userland to the kernel.  There's no
sysctl tree in the kernel that can be readily exported as a nvlist -
the kernel would need to iterate through the hierarchy and build the
tree.  The only advantage of this approach is that a client only needs
to perform a single syscall.  IMO, this is the wrong approach - where
practical, functionality should be in userland, not in the kernel.

-- 
Peter Jeremy
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