Note the gathered statistics. One CAVEAT down.

share/man/man4/acpicpu.4

@@ -1,4 +1,4 @@
-.\" $NetBSD: acpicpu.4,v 1.5 2010/08/09 16:13:21 jruoho Exp $
+.\" $NetBSD: acpicpu.4,v 1.6 2010/08/10 02:43:50 jruoho Exp $
 .\"
 .\" Coyright (c) 2010 Jukka Ruohonen <jruohonen@iki.fi>
 .\" All rights reserved.
@@ -24,7 +24,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd August 9, 2010
+.Dd August 10, 2010
 .Dt ACPICPU 4
 .Os
 .Sh NAME
@@ -186,6 +186,16 @@ Currently the
 implementation reacts to these events by imposing the dynamic maximum, but
 .Nm
 does not take any actions to manipulate the frequencies by itself.
+.Ss Statistics
+The
+.Nm
+driver uses event counters to track the times
+a processor has entered a given state.
+It is possible to view the statistics by using
+.Xr vmstat 1
+(with the argument
+.Ar -e ) .
+Note that valid per-CPU data is available only for C-states.
 .Sh SEE ALSO
 .Xr acpi 4 ,
 .Xr cpu_idle 9
@@ -237,11 +247,4 @@ for different policies.
 It is only possible to control the
 .Tn CPU
 frequencies from userland.
-.It
-There are currently no proper ways to export
-statistical and other information from
-.Nm .
-This applies to
-.Tn ACPI
-generally.
 .El