MFC r315362,r315363,r315365:

r315362:

Capitalize .Dt macro argument

By convention, per mdoc(7), the document title should be all caps.

r315363:

Fix manlint errors

- Add missing comma after kvm_dpcpu_setcpu .Nm macro use (multiple
.Nm entries should be separated by commas)
- Add missing section for kvm_dpcpu_setcpu Xr.

r315365:

Tweak r315363 slightly

I noticed after commit that kvm_dpcpu_setcpu was defined in the manpage.
Thus, the correct macro for the function reference is .Fn, not .Xr.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add kvm_getncpus() to obtain mp_ncpus.

Sponsored by: Nginx, Inc.

While it isn't too late and kvm_read_zpcpu() function isn't yet used
outside libkvm(3), change its order of arguments, so that it is the
same as in kvm_read().

Sponsored by: Nginx, Inc.

Remove EOL whitespace.

o Provide function kvm_read_zpcpu() to access UMA_ZONE_PCPU allocations.
o Provide function kvm_counter_u64_fetch() to fetch valut of a counter(9).

Sponsored by: Nginx, Inc.

General mdoc(7) and typo fixes.

PR: 167734
Submitted by: Nobuyuki Koganemaru (kogane!jp.freebsd.org)
MFC after: 3 days

Fix several typos in macros or macro misusage.

Found by: make manlint
Reviewed by: ru
Approved by: philip (mentor)

A first cut at teaching libkvm how to deal with dynamic per-CPU storage
(DPCPU):

A new API, kvm_dpcpu_setcpu(3), selects the active CPU for the purposes
of DPCPU. Calls to kvm_nlist(3) will automatically translate DPCPU
symbols and return a pointer to the current CPU's version of the data.
Consumers needing to read the same symbol on several CPUs will invoke a
series of setcpu/nlist calls, one per CPU of interest.

This addition makes it possible for tools like netstat(1) to query the
values of DPCPU variables during crashdump analysis, and is based on
similar code handling virtualized global variables.

MFC after: 1 week
Sponsored by: Juniper Networks, Inc.

Add a "CACHING" section regarding the internal caching of kernel variables
and the ability to clear that cache.

Add two new routines to libkvm for working with per-CPU data:
kvm_getmaxcpu() and kvm_getpcpu().

MFC after: 1 week