Merge branch 'jn/supervisor_child_count_only' into ccase/r13b04_dev

* jn/supervisor_child_count_only:
  Add count_children/1 to supervisor.erl to determine the number of

OTP-8436  Added supervisor:count_children/1 to count the number of children
          being managed without the memory impact of which_children/1.
          (Thanks to Jay Nelson.)

1 files changed, 40 insertions, 4 deletions

diff --git a/lib/stdlib/doc/src/supervisor.xml b/lib/stdlib/doc/src/supervisor.xml
index adf9d24eae..c696434d49 100644
--- a/lib/stdlib/doc/src/supervisor.xml
+++ b/lib/stdlib/doc/src/supervisor.xml
@@ -4,7 +4,7 @@
 <erlref>
   <header>
     <copyright>
-      <year>1996</year><year>2009</year>
+      <year>1996</year><year>2010</year>
       <holder>Ericsson AB. All Rights Reserved.</holder>
     </copyright>
     <legalnotice>
@@ -13,12 +13,12 @@
       compliance with the License. You should have received a copy of the
       Erlang Public License along with this software. If not, it can be
       retrieved online at http://www.erlang.org/.
-    
+
       Software distributed under the License is distributed on an "AS IS"
       basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
       the License for the specific language governing rights and limitations
       under the License.
-    
+
     </legalnotice>
 
     <title>supervisor</title>
@@ -402,9 +402,12 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules}
         <v>&nbsp;Module = atom()</v>
       </type>
       <desc>
-        <p>Returns a list with information about all child
+        <p>Returns a newly created list with information about all child
           specifications and child processes belonging to
           the supervisor <c>SupRef</c>.</p>
+        <p>Note that calling this function when supervising a large
+          number of children under low memory conditions can cause an
+          out of memory exception.</p>
         <p>See <c>start_child/2</c> for a description of <c>SupRef</c>.</p>
         <p>The information given for each child specification/process
           is:</p>
@@ -428,6 +431,39 @@ child_spec() = {Id,StartFunc,Restart,Shutdown,Type,Modules}
       </desc>
     </func>
     <func>
+      <name>count_children(SupRef) -> PropListOfCounts</name>
+      <fsummary>Return counts for the number of childspecs, active children, supervisors and workers.</fsummary>
+      <type>
+        <v>SupRef = Name | {Name,Node} | {global,Name} | pid()</v>
+        <v>&nbsp;Name = Node = atom()</v>
+        <v>PropListOfCounts = [{specs, ChildSpecCount}, {active, ActiveProcessCount}, {supervisors, ChildSupervisorCount}, {workers, ChildWorkerCount}]</v>
+      </type>
+      <desc>
+        <p>Returns a property list (see <c>proplists</c>) containing the
+          counts for each of the following elements of the supervisor's
+          child specifications and managed processes:</p>
+        <list type="bulleted">
+          <item>
+            <p><c>specs</c> - the total count of children, dead or alive.</p>
+          </item>
+          <item>
+            <p><c>active</c> - the count of all actively running child processes
+              managed by this supervisor.</p>
+          </item>
+          <item>
+            <p><c>supervisors</c> - the count of all children marked as
+              child_type = supervisor in the spec list, whether or not the
+              child process is still alive.</p>
+          </item>
+          <item>
+            <p><c>workers</c> - the count of all children marked as
+              child_type = worker in the spec list, whether or not the child
+              process is still alive.</p>
+          </item>
+        </list>
+      </desc>
+    </func>
+    <func>
       <name>check_childspecs([ChildSpec]) -> Result</name>
       <fsummary>Check if children specifications are syntactically correct.</fsummary>
       <type>