man: update ManagedOOMPreference entry to reflect new behavior

diff --git a/man/systemd.resource-control.xml b/man/systemd.resource-control.xml
index 940395a44276a6e7068e9751d1c0824837c183a9..2b1c20b96e263cb92fd54609371f8e34f0ad5d92 100644 (file)
--- a/man/systemd.resource-control.xml
+++ b/man/systemd.resource-control.xml
@@ -1077,9 +1077,20 @@ DeviceAllow=/dev/loop-control
           <para>Allows deprioritizing or omitting this unit's cgroup as a candidate when
           <command>systemd-oomd</command> needs to act. Requires support for extended attributes (see
           <citerefentry project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
-          in order to use <option>avoid</option> or <option>omit</option>. Additionally,
-          <command>systemd-oomd</command> will ignore these extended attributes if the unit's cgroup is not
-          owned by the root user.</para>
+          in order to use <option>avoid</option> or <option>omit</option>.</para>
+
+          <para>When calculating candidates to relieve swap usage, <command>systemd-oomd</command> will
+          only respect these extended attributes if the unit's cgroup is owned by root.</para>
+
+          <para>When calculating candidates to relieve memory pressure, <command>systemd-oomd</command>
+          will only respect these extended attributes if the unit's cgroup owner, and the
+          owner of the monitored ancestor cgroup are the same. For example, if <command>systemd-oomd</command>
+          is calculating candidates for <filename>-.slice</filename>, then extended attributes set
+          on descendants of <filename>/user.slice/user-1000.slice/user@1000.service/</filename>
+          will be ignored because the descendants are owned by UID 1000, and <filename>-.slice</filename>
+          is owned by UID 0. But, if calculating candidates for
+          <filename>/user.slice/user-1000.slice/user@1000.service/</filename>, then extended attributes set
+          on the descendants would be respected.</para>
 
           <para>If this property is set to <option>avoid</option>, the service manager will convey this to
           <command>systemd-oomd</command>, which will only select this cgroup if there are no other viable