From d784a8d474a7e9c421a7b44530612e91c8764627 Mon Sep 17 00:00:00 2001
From: Oleg Solovyov <mcpain@altlinux.org>
Date: Tue, 2 Aug 2022 10:10:54 +0300
Subject: [PATCH] oomd: notify via dbus what have been killed

---
 man/org.freedesktop.oom1.xml | 31 ++++++++++++++++++++++++++++++-
 src/oom/oomd-manager-bus.c   |  5 +++++
 src/oom/oomd-manager.c       | 24 ++++++++++++++++++++++--
 3 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/man/org.freedesktop.oom1.xml b/man/org.freedesktop.oom1.xml
index 838eb6738d..c6b8c7fb3d 100644
--- a/man/org.freedesktop.oom1.xml
+++ b/man/org.freedesktop.oom1.xml
@@ -39,6 +39,9 @@ node /org/freedesktop/oom1 {
   interface org.freedesktop.oom1.Manager {
     methods:
       DumpByFileDescriptor(out h fd);
+    signals:
+      Killed(s cgroup,
+             s reason);
   };
   interface org.freedesktop.DBus.Peer { ... };
   interface org.freedesktop.DBus.Introspectable { ... };
@@ -56,12 +59,38 @@ node /org/freedesktop/oom1 {
 
     <variablelist class="dbus-method" generated="True" extra-ref="DumpByFileDescriptor()"/>
 
+    <variablelist class="dbus-signal" generated="True" extra-ref="Killed"/>
+
     <!--End of Autogenerated section-->
 
     <refsect2>
       <title>Methods</title>
 
-      <para>...</para>
+      <para><function>Killed</function> signal is sent when any cgroup is killed by oomd.</para>
+      <para>Note that more reasons will be added in the future, and the table below will be expanded accordingly.</para>
+      <table>
+        <title>Killing reasons</title>
+        <tgroup cols="2" align="left" colsep="1" rowsep="1">
+        <colspec colname="reason"/>
+        <colspec colname="description"/>
+        <thead>
+          <row>
+            <entry>Reason</entry>
+            <entry>Description</entry>
+          </row>
+        </thead>
+        <tbody>
+          <row>
+            <entry>memory-used</entry>
+            <entry>Application took too much memory and swap.</entry>
+          </row>
+          <row>
+            <entry>memory-pressure</entry>
+            <entry>Application took enough memory and swap to cause sufficient slowdown of other applications.</entry>
+          </row>
+        </tbody>
+        </tgroup>
+      </table>
     </refsect2>
   </refsect1>
 
diff --git a/src/oom/oomd-manager-bus.c b/src/oom/oomd-manager-bus.c
index b41e366309..f4c196ee10 100644
--- a/src/oom/oomd-manager-bus.c
+++ b/src/oom/oomd-manager-bus.c
@@ -38,6 +38,11 @@ static const sd_bus_vtable manager_vtable[] = {
                                  SD_BUS_PARAM(fd),
                                  bus_method_dump_by_fd,
                                  SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_SIGNAL_WITH_NAMES("Killed",
+                                 "ss",
+                                 SD_BUS_PARAM(cgroup)
+                                 SD_BUS_PARAM(reason),
+                                 0),
         SD_BUS_VTABLE_END
 };
 
diff --git a/src/oom/oomd-manager.c b/src/oom/oomd-manager.c
index e49eef6577..d9574fa97b 100644
--- a/src/oom/oomd-manager.c
+++ b/src/oom/oomd-manager.c
@@ -410,7 +410,7 @@ static int monitor_swap_contexts_handler(sd_event_source *s, uint64_t usec, void
                 if (r < 0)
                         log_notice_errno(r, "Failed to kill any cgroup(s) based on swap: %m");
                 else {
-                        if (selected && r > 0)
+                        if (selected && r > 0) {
                                 log_notice("Killed %s due to memory used (%"PRIu64") / total (%"PRIu64") and "
                                            "swap used (%"PRIu64") / total (%"PRIu64") being more than "
                                            PERMYRIAD_AS_PERCENT_FORMAT_STR,
@@ -418,6 +418,16 @@ static int monitor_swap_contexts_handler(sd_event_source *s, uint64_t usec, void
                                            m->system_context.mem_used, m->system_context.mem_total,
                                            m->system_context.swap_used, m->system_context.swap_total,
                                            PERMYRIAD_AS_PERCENT_FORMAT_VAL(m->swap_used_limit_permyriad));
+
+                                /* send dbus signal */
+                                (void) sd_bus_emit_signal(m->bus,
+                                                          "/org/freedesktop/oom1",
+                                                          "org.freedesktop.oom1.Manager",
+                                                          "Killed",
+                                                          "ss",
+                                                          selected,
+                                                          "memory-used");
+                        }
                         return 0;
                 }
         }
@@ -524,13 +534,23 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
                                  * it. In either case, go through the event loop again and select a new candidate if
                                  * pressure is still high. */
                                 m->mem_pressure_post_action_delay_start = usec_now;
-                                if (selected && r > 0)
+                                if (selected && r > 0) {
                                         log_notice("Killed %s due to memory pressure for %s being %lu.%02lu%% > %lu.%02lu%%"
                                                    " for > %s with reclaim activity",
                                                    selected, t->path,
                                                    LOADAVG_INT_SIDE(t->memory_pressure.avg10), LOADAVG_DECIMAL_SIDE(t->memory_pressure.avg10),
                                                    LOADAVG_INT_SIDE(t->mem_pressure_limit), LOADAVG_DECIMAL_SIDE(t->mem_pressure_limit),
                                                    FORMAT_TIMESPAN(m->default_mem_pressure_duration_usec, USEC_PER_SEC));
+
+                                        /* send dbus signal */
+                                        (void) sd_bus_emit_signal(m->bus,
+                                                                  "/org/freedesktop/oom1",
+                                                                  "org.freedesktop.oom1.Manager",
+                                                                  "Killed",
+                                                                  "ss",
+                                                                  selected,
+                                                                  "memory-pressure");
+                                }
                                 return 0;
                         }
                 }