Setting oom_score_adj directly is faster and doesn't have to involve debugd when ARC++ is disabled.

Bug: 868249
Change-Id: Ie99e4c4ac7738c369a9b54bf2621a2c16dc8bc1d
Reviewed-on: https://chromium-review.googlesource.com/1168222Reviewed-by: Cheng-Yu Lee <cylee@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: Cheng-Yu Lee <cylee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582431}

base/process/memory_linux.cc

@@ -15,6 +15,7 @@
 #include "base/logging.h"
 #include "base/process/internal_linux.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 
 #if defined(USE_TCMALLOC)
@@ -65,15 +66,30 @@ void EnableTerminationOnOutOfMemory() {
 #endif
 }
 
-// NOTE: This is not the only version of this function in the source:
-// the setuid sandbox (in process_util_linux.c, in the sandbox source)
-// also has its own C version.
-bool AdjustOOMScore(ProcessId process, int score) {
+// ScopedAllowBlocking() has private constructor and it can only be used in
+// friend classes/functions. Declaring a class is easier in this situation to
+// avoid adding more dependency to thread_restrictions.h because of the
+// parameter used in AdjustOOMScore(). Specifically, ProcessId is a typedef
+// and we'll need to include another header file in thread_restrictions.h
+// without the class.
+class AdjustOOMScoreHelper {
+ public:
+  static bool AdjustOOMScore(ProcessId process, int score);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(AdjustOOMScoreHelper);
+};
+
+// static.
+bool AdjustOOMScoreHelper::AdjustOOMScore(ProcessId process, int score) {
   if (score < 0 || score > kMaxOomScore)
     return false;
 
   FilePath oom_path(internal::GetProcPidDir(process));
 
+  // Temporarily allowing blocking since oom paths are pseudo-filesystem paths.
+  base::ScopedAllowBlocking allow_blocking;
+
   // Attempt to write the newer oom_score_adj file first.
   FilePath oom_file = oom_path.AppendASCII("oom_score_adj");
   if (PathExists(oom_file)) {
@@ -102,6 +118,13 @@ bool AdjustOOMScore(ProcessId process, int score) {
   return false;
 }
 
+// NOTE: This is not the only version of this function in the source:
+// the setuid sandbox (in process_util_linux.c, in the sandbox source)
+// also has its own C version.
+bool AdjustOOMScore(ProcessId process, int score) {
+  return AdjustOOMScoreHelper::AdjustOOMScore(process, score);
+}
+
 bool UncheckedMalloc(size_t size, void** result) {
 #if BUILDFLAG(USE_ALLOCATOR_SHIM)
   *result = allocator::UncheckedAlloc(size);

base/threading/thread_restrictions.h

@@ -149,6 +149,7 @@ namespace internal {
 class TaskTracker;
 }
 
+class AdjustOOMScoreHelper;
 class GetAppOutputScopedAllowBaseSyncPrimitives;
 class SimpleThread;
 class StackSamplingProfiler;
@@ -250,6 +251,7 @@ class BASE_EXPORT ScopedAllowBlocking {
   // This can only be instantiated by friends. Use ScopedAllowBlockingForTesting
   // in unit tests to avoid the friend requirement.
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest, ScopedAllowBlocking);
+  friend class AdjustOOMScoreHelper;
   friend class android_webview::ScopedAllowInitGLBindings;
   friend class audio::OutputDevice;
   friend class content::BrowserProcessSubThread;

chrome/browser/resource_coordinator/tab_manager_delegate_chromeos.cc

@@ -18,6 +18,7 @@
 #include "base/files/file_util.h"
 #include "base/memory/memory_pressure_monitor_chromeos.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/process/memory.h"
 #include "base/process/process_handle.h"  // kNullProcessHandle.
 #include "base/process/process_metrics.h"
 #include "base/strings/string16.h"
@@ -380,10 +381,10 @@ void TabManagerDelegate::OnFocusTabScoreAdjustmentTimeout() {
   // Sets OOM score.
   VLOG(3) << "Set OOM score " << chrome::kLowestRendererOomScore
           << " for focused tab " << pid;
-  std::map<int, int> dict;
-  dict[pid] = chrome::kLowestRendererOomScore;
-  DCHECK(GetDebugDaemonClient());
-  GetDebugDaemonClient()->SetOomScoreAdj(dict, base::Bind(&OnSetOomScoreAdj));
+  if (!base::AdjustOOMScore(pid, chrome::kLowestRendererOomScore))
+    LOG(ERROR) << "Failed to set oom_score_adj to "
+               << chrome::kLowestRendererOomScore
+               << " for focused tab, pid: " << pid;
 }
 
 void TabManagerDelegate::AdjustFocusedTabScore(base::ProcessHandle pid) {
@@ -760,7 +761,13 @@ void TabManagerDelegate::DistributeOomScoreInRange(
     // current cached score.
     if (oom_score_map_[pid] != score) {
       VLOG(3) << "Update OOM score " << score << " for " << *cur;
-      oom_scores_to_change[pid] = static_cast<int32_t>(score);
+      if (cur->app()) {
+        oom_scores_to_change[pid] = static_cast<int32_t>(score);
+      } else {
+        if (!base::AdjustOOMScore(pid, score))
+          LOG(ERROR) << "Failed to set oom_score_adj to " << score
+                     << " for process " << pid;
+      }
     }
     priority += priority_increment;
   }