Linux: Adjust /proc/pid/oom_adj to sacrifice plugin and renderer processes to the OOM killer.

BUG=29752
TEST=During out of memory conditions, Linux kernel picks a plugin/renderer over the browser process.
Review URL: http://codereview.chromium.org/467058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@34222 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 23 insertions, 2 deletions

diff --git a/base/process_util.h b/base/process_util.h
index 41d1d17..1122de7 100644
--- a/base/process_util.h
+++ b/base/process_util.h
@@ -100,6 +100,13 @@ FilePath GetProcessExecutablePath(ProcessHandle process);
 // CPU-related ticks.  Returns -1 on parse error.
 // Exposed for testing.
 int ParseProcStatCPU(const std::string& input);
+
+static const char kAdjustOOMScoreSwitch[] = "--adjust-oom-score";
+
+// This adjusts /proc/process/oom_adj so the Linux OOM killer will prefer
+// certain process types over others. The range for the adjustment is
+// [-17,15], with [0,15] being user accessible.
+bool AdjustOOMScore(ProcessId process, int score);
 #endif
 
 #if defined(OS_POSIX)
diff --git a/base/process_util_linux.cc b/base/process_util_linux.cc
index bd6bcf3..1a7e090 100644
--- a/base/process_util_linux.cc
+++ b/base/process_util_linux.cc
@@ -513,7 +513,6 @@ void OnNoMemory() {
 }  // namespace
 
 extern "C" {
-
 #if !defined(LINUX_USE_TCMALLOC)
 
 typedef void* (*malloc_type)(size_t size);
@@ -600,7 +599,6 @@ int posix_memalign(void** ptr, size_t alignment, size_t size) {
 }
 
 #endif  // !defined(LINUX_USE_TCMALLOC)
-
 }  // extern C
 
 void EnableTerminationOnOutOfMemory() {
@@ -610,4 +608,20 @@ void EnableTerminationOnOutOfMemory() {
   // malloc and friends and make them die on out of memory.
 }
 
+bool AdjustOOMScore(ProcessId process, int score) {
+  if (score < 0 || score > 15)
+    return false;
+
+  FilePath oom_adj("/proc");
+  oom_adj = oom_adj.Append(Int64ToString(process));
+  oom_adj = oom_adj.AppendASCII("oom_adj");
+
+  if (!file_util::PathExists(oom_adj))
+    return false;
+
+  std::string score_str = IntToString(score);
+  return (static_cast<int>(score_str.length()) ==
+          file_util::WriteFile(oom_adj, score_str.c_str(), score_str.length()));
+}
+
 }  // namespace base