sample.conf: update with cgroup help and examples

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/sample.conf

@@ -1,4 +1,12 @@
-# sample.conf: template run/task/service stanza for finit
+# sample.conf: template cgroup/run/task/service stanza for finit
+#
+# The top-level cgroups can be defined anywhere, but share the same
+# namespace.  It is up to the user to ensure groups are defined only
+# once, otherwise the last read .conf wins.  See below for assigning
+# run/task/services to cgroups.  The below example creates the cgroup
+# NAME with the following cpu and memory settings:
+#
+#   cgroup NAME cpu.weight:1000 mem.max:65
 #
 # The one-shot commands 'run' and 'task' are called only once per
 # runlevel.  Finit does not restart them when they exit.
@@ -25,6 +33,16 @@
 # |       |       `--------------------------------------------------------------- Optional conditions
 # |        `---------------------------------------------------------------------- Optional Runlevels
 #  `------------------------------------------------------------------------------ Monitored application
+#
+# Each stanza can also hold a 'cgroup' argument, or be prefixed with
+# cgroup.NAME to place all following stanzas in the same group.  In
+# the following example, foo and bar share the cgroup foo but baz
+# runs in its own cgroup baz:
+#
+#   cgroup.foo
+#   service cgroup:cpu.weight:250,mem.max:655350 foo args -- foo desc
+#   service cgroup:cpu.weight:150,mem.max:655350 bar args -- bar desc
+#   service cgroup.baz:cpu.weight:300 baz args -- baz desc
 
 # Debian GNU/Linux: start SSH daemon as soon as basic networking comes up
 #service [2345] <net/lo/up> env:-/etc/default/ssh /usr/sbin/sshd -D $SSHD_OPTS -- OpenSSH daemon
@@ -33,11 +51,11 @@
 #task [S] env:/etc/conf.d/loadkmap zcat $KEYMAP | loadkmap -- Loading keymap
 
 # Alpine Linux: start SSH daemon with $DROPBEAR_OPTS from /etc/conf.d
-#service [2345] env:-/etc/conf.d/dropbear dropbear -R -F $DROPBEAR_OPTS -- Dropbear SSH daemon
+#service [2345] cgroup.user env:-/etc/conf.d/dropbear dropbear -R -F $DROPBEAR_OPTS -- Dropbear SSH daemon
 
 # Handle PWR button to shutdown/reboot -- useful in Qemu (virt-manager)
 # Depends on syslogd having started. Redirect any output to log.
-#service [2345] <pid/syslogd> log acpid -f -- ACPI daemon
+#service [2345] <pid/syslogd> cgroup:mem.max:32000,cpu.max:1000 log acpid -f -- ACPI daemon
 
 # Start rsyslogd as soon as possible, should always run
 # Provides pid/syslogd condition