[src/pgoyette-localcount]: src/share/man/man9 Add a bit more about appropriat...

[pgoyette <pgoyette%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3cbcd720c873
branches:  pgoyette-localcount
changeset: 852796:3cbcd720c873
user:      pgoyette <pgoyette%NetBSD.org@localhost>
date:      Sat Jul 16 23:13:59 2016 +0000

description:
Add a bit more about appropriate use-cases.

diffstat:

 share/man/man9/localcount.9 |  10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diffs (24 lines):

diff -r 2223415e77c1 -r 3cbcd720c873 share/man/man9/localcount.9
--- a/share/man/man9/localcount.9       Sat Jul 16 22:35:34 2016 +0000
+++ b/share/man/man9/localcount.9       Sat Jul 16 23:13:59 2016 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: localcount.9,v 1.1.2.1 2016/07/16 09:36:57 pgoyette Exp $
+.\"    $NetBSD: localcount.9,v 1.1.2.2 2016/07/16 23:13:59 pgoyette Exp $
 .\"
 .\" Copyright (c) 2016
 .\" All rights reserved.
@@ -74,6 +74,14 @@
 .Xr atomic_ops 3
 and almost always more than
 .Xr psref 9 .
+.Pp
+As a rough heuristic,
+.Nm
+should be used for classes of objects of which there are maybe a few dozen
+instances but not a few thousand instances (e.g. autoconf devices, but not
+network flows) and on which there may be a mixture of long-term I/O waits,
+such as xyzread for a device xyz(4), and short-term fast operations, such as
+xyzioctl(IOC_READ_A_CPU_REG).
 .Sh FUNCTIONS
 .Bl -tag -width abcd
 .It Fn localcount_init "lc"