MFH revisions 242743 to 243202:

Make parameters to -c and -k options optional.  If no parameters are
supplied, print information for all keywords.

Improve output of -c option, in particular in conjunction with -k
option.

Complete man page.

Add comment on standards conformity.


git-svn-id: svn://svn.freebsd.org/base/stable/9@250905 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r250327

Add a sysctl vfs.read_min to complement the exiting vfs.read_max.  It
defaults to 1, meaning that it's off.

When read-ahead is enabled on a file, the vfs cluster code deliberately
breaks a read into 2 I/O transactions; one to satisfy the actual read,
and one to perform read-ahead.  This makes sense in low-latency
circumstances, but often produces unbalanced i/o transactions that
penalize disks.  By setting vfs.read_min, we can tell the algorithm to
fetch a larger transaction that what we asked for, achieving the same
effect as the read-ahead but without the doubled, unbalanced transaction
and the slightly lower latency.  This significantly helps our workloads
with video streaming.

Submitted by:   emax
Reviewed by:    kib
Obtained from:  Netflix


git-svn-id: svn://svn.freebsd.org/base/stable/9@250906 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r248830, r250027, r250409

Submitted by:	gibbs, andre, kib
Obtained from:	Netflix


git-svn-id: svn://svn.freebsd.org/base/stable/9@250907 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r250804:

  Refine the "nojail" rc keyword, adding "nojailvnet" for files that don't
  apply to most jails but do apply to vnet jails.  This includes adding
  a new sysctl "security.jail.vnet" to identify vnet jails.

PR:		conf/149050
Submitted by:	mdodd


git-svn-id: svn://svn.freebsd.org/base/stable/9@250915 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Merge remote-tracking branch 'upstream/svn_stable_9' into svn_stable_9