TabManager: Add more logs to understand how it works when memory is low.

chrome/browser/memory/tab_manager_delegate_chromeos.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/memory/tab_manager_delegate_chromeos.h"
 
 #include <math.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 103 matching lines @@
     default:
       return os << "NOT_IMPLEMENTED_ERROR";
   }
   return os;
 }
 
 // TabManagerDelegate::Candidate implementation.
 std::ostream& operator<<(
     std::ostream& out, const TabManagerDelegate::Candidate& candidate) {
   if (candidate.app()) {
-    out << "app " << candidate.app()->pid() << " ("
-        << candidate.app()->process_name() << ")"
-        << ", process_state " << candidate.app()->process_state()
-        << ", is_focused " << candidate.app()->is_focused()
-        << ", lastActivityTime " << candidate.app()->last_activity_time();
+    out << "app " << *candidate.app();
   } else if (candidate.tab()) {
-    out << "tab " << candidate.tab()->renderer_handle;
+    const TabStats* const& tab = candidate.tab();
+    out << "tab " << tab->title << ", renderer_handle: " << tab->renderer_handle
+        << ", oom_score: " << tab->oom_score
+        << ", is_discarded: " << tab->is_discarded
+        << ", discard_count: " << tab->discard_count
+        << ", last_active: " << tab->last_active;
   }
   out << ", process_type " << candidate.process_type();
   return out;
 }
 
 TabManagerDelegate::Candidate& TabManagerDelegate::Candidate::operator=(
     TabManagerDelegate::Candidate&& other) {
   tab_ = other.tab_;
   app_ = other.app_;
   process_type_ = other.process_type_;
@@ skipping 443 matching lines @@
     const std::vector<arc::ArcProcess>& arc_processes) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   VLOG(2) << "LowMemoryKillImpl";
 
   const std::vector<TabManagerDelegate::Candidate> candidates =
       GetSortedCandidates(tab_list, arc_processes);
 
   int target_memory_to_free_kb = mem_stat_->TargetMemoryToFreeKB();
   const TimeTicks now = TimeTicks::Now();
 
+  MEMORY_LOG(ERROR) << "List of low memory kill candidates "
+                       "(sorted from low priority to high priority):";
+  for (auto it = candidates.rbegin(); it != candidates.rend(); ++it) {
+    MEMORY_LOG(ERROR) << *it;
+  }
   // Kill processes until the estimated amount of freed memory is sufficient to
   // bring the system memory back to a normal level.
   // The list is sorted by descending importance, so we go through the list
   // backwards.
   for (auto it = candidates.rbegin(); it != candidates.rend(); ++it) {
     MEMORY_LOG(ERROR) << "Target memory to free: " << target_memory_to_free_kb
                       << " KB";
     if (target_memory_to_free_kb <= 0)
       break;
     // Never kill selected tab, foreground app, and important apps regardless of
     // whether they're in the active window. Since the user experience would be
     // bad.
     ProcessType process_type = it->process_type();
     if (process_type <= ProcessType::IMPORTANT_APP) {
-      MEMORY_LOG(ERROR) << "Skipped killing " << *it;
+      MEMORY_LOG(ERROR) << "Skipped killing " << it->app()->process_name();
       continue;
     }
     if (it->app()) {
       if (IsRecentlyKilledArcProcess(it->app()->process_name(), now)) {
-        MEMORY_LOG(ERROR) << "Avoided killing " << *it << " too often";
+        MEMORY_LOG(ERROR) << "Avoided killing " << it->app()->process_name()
+                          << " too often";
         continue;
       }
       int estimated_memory_freed_kb =
           mem_stat_->EstimatedMemoryFreedKB(it->app()->pid());
       if (KillArcProcess(it->app()->nspid())) {
         recently_killed_arc_processes_[it->app()->process_name()] = now;
         target_memory_to_free_kb -= estimated_memory_freed_kb;
         MemoryKillsMonitor::LogLowMemoryKill("APP", estimated_memory_freed_kb);
-        MEMORY_LOG(ERROR) << "Killed " << *it << ", estimated "
-                          << estimated_memory_freed_kb << " KB freed";
+        MEMORY_LOG(ERROR) << "Killed app " << it->app()->process_name() << " ("
+                          << it->app()->pid() << ")"
+                          << ", estimated " << estimated_memory_freed_kb
+                          << " KB freed";
       } else {
-        MEMORY_LOG(ERROR) << "Failed to kill " << *it;
+        MEMORY_LOG(ERROR) << "Failed to kill " << it->app()->process_name();
       }
     } else {
       int64_t tab_id = it->tab()->tab_contents_id;
       // The estimation is problematic since multiple tabs may share the same
       // process, while the calculation counts memory used by the whole process.
       // So |estimated_memory_freed_kb| is an over-estimation.
       int estimated_memory_freed_kb =
           mem_stat_->EstimatedMemoryFreedKB(it->tab()->renderer_handle);
       if (KillTab(tab_id)) {
         target_memory_to_free_kb -= estimated_memory_freed_kb;
         MemoryKillsMonitor::LogLowMemoryKill("TAB", estimated_memory_freed_kb);
-        MEMORY_LOG(ERROR) << "Killed " << *it << ", estimated "
+        MEMORY_LOG(ERROR) << "Killed tab " << it->tab()->title << " ("
+                          << it->tab()->renderer_handle << "), estimated "
                           << estimated_memory_freed_kb << " KB freed";
       }
     }
   }
   if (target_memory_to_free_kb > 0) {
     MEMORY_LOG(ERROR)
         << "Unable to kill enough candidates to meet target_memory_to_free_kb ";
   }
 }
 
@@ skipping 122 matching lines @@
     priority += priority_increment;
   }
 
   if (oom_scores_to_change.size()) {
     GetDebugDaemonClient()->SetOomScoreAdj(
         oom_scores_to_change, base::Bind(&OnSetOomScoreAdj));
   }
 }
 
 }  // namespace memory