Dumping memory.stat in oomd

Summary:
Commit [1 / 3]

Dumps the memory.stat of a cgroup to OLOG before killing the cgroup.

Reviewed By: lnyng

Differential Revision: D62042595

fbshipit-source-id: 3048a528f8b0198d0794feb955bae77a388f76ee

src/oomd/plugins/BaseKillPlugin.cpp

@@ -443,6 +443,20 @@ int BaseKillPlugin::getAndTryToKillPids(const CgroupContext& target) {
   return nrKilled;
 }
 
+int BaseKillPlugin::dumpMemoryStat(const CgroupContext& target) {
+  auto stats =
+      Fs::readFileByLine(Fs::Fd::openat(target.fd(), Fs::kMemStatFile));
+  if (!stats) {
+    return 1;
+  }
+  OLOG << "memory.stat for " + target.cgroup().relativePath() + ": ";
+  for (auto& line : *stats) {
+    OLOG << line;
+  }
+
+  return 0;
+}
+
 int BaseKillPlugin::tryToKillCgroup(
     const CgroupContext& target,
     const KillUuid& killUuid,
@@ -462,8 +476,13 @@ int BaseKillPlugin::tryToKillCgroup(
 
   OLOG << "Trying to kill " << cgroupPath;
 
+  if (dumpMemoryStat(target)) {
+    OLOG << "Failed to open " << cgroupPath << "/memory.stat";
+  }
+
   reportKillUuidToXattr(cgroupPath, killUuid);
   reportKillInitiationToXattr(cgroupPath);
+
   while (tries--) {
     // Descendent cgroups created during killing will be missed because
     // getAndTryToKillPids reads cgroup children from OomdContext's cache

src/oomd/plugins/BaseKillPlugin.h

@@ -190,6 +190,7 @@ class BaseKillPlugin : public Engine::BasePlugin {
    * Override point for tests to control the clock
    */
   virtual bool pastPrekillHookTimeout(const OomdContext& ctx) const;
+  virtual int dumpMemoryStat(const CgroupContext& target);
 
  private:
   virtual int getAndTryToKillPids(const CgroupContext& target);

src/oomd/plugins/CorePluginsTest.cpp

@@ -48,6 +48,14 @@ std::unique_ptr<Engine::BasePlugin> createPlugin(const std::string& name) {
 namespace Oomd {
 class BaseKillPluginMock : public BaseKillPlugin {
  public:
+  /*
+   * We don't actually need to dump memory.stat since we won't
+   * actually be killing any live processes
+   */
+  int dumpMemoryStat(const CgroupContext&) override {
+    return 0;
+  }
+
   int tryToKillPids(const std::vector<int>& pids) override {
     int ret = 0;
     killed.reserve(pids.size());
@@ -58,7 +66,6 @@ class BaseKillPluginMock : public BaseKillPlugin {
         ++ret;
       }
     }
-
     return ret;
   }