Changing OOM range to 0, 1000 and tweaking OOM algorithm.

With this change, we now use the newer oom_score_adj file (with
fallback to oom_adj when on a system that doesn't support it) so that
we can take advantage of a finer range ([0, 1000] instead of [0, 15]).

Also tweaked the OOM priority manager to prioritize things in a
slightly different order, preferring (even more) not to kill tabs that
the user has currently selected.

BUG=chromium-os:18421, chromium:65009
TEST=Ran on device, observed OOM adj values, forced OOM conditions to
     watch kills.

Review URL: http://codereview.chromium.org/7671033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@97724 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 33 insertions, 13 deletions

diff --git a/sandbox/linux/suid/process_util.h b/sandbox/linux/suid/process_util.h
index 6bab897..1826555 100644
--- a/sandbox/linux/suid/process_util.h
+++ b/sandbox/linux/suid/process_util.h
@@ -13,11 +13,14 @@
 
 #include "base/base_export.h"
 
-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.
+// This adjusts /proc/process/oom_score_adj so the Linux OOM killer
+// will prefer certain process types over others. The range for the
+// adjustment is [-1000, 1000], with [0, 1000] being user accessible.
+//
+// If the Linux system isn't new enough to use oom_score_adj, then we
+// try to set the older oom_adj value instead, scaling the score to
+// the required range of [0, 15]. This may result in some aliasing of
+// values, of course.
 BASE_EXPORT bool AdjustOOMScore(pid_t process, int score);
 
 #endif  // SANDBOX_LINUX_SUID_PROCESS_UTIL_H_
diff --git a/sandbox/linux/suid/process_util_linux.c b/sandbox/linux/suid/process_util_linux.c
index 17453de..13f45ce 100644
--- a/sandbox/linux/suid/process_util_linux.c
+++ b/sandbox/linux/suid/process_util_linux.c
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -19,8 +19,13 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+// Ranges for the current (oom_score_adj) and previous (oom_adj)
+// flavors of OOM score.
+static const int kMaxOomScore = 1000;
+static const int kMaxOldOomScore = 15;
+
 bool AdjustOOMScore(pid_t process, int score) {
-  if (score < 0 || score > 15)
+  if (score < 0 || score > kMaxOomScore)
     return false;
 
   char oom_adj[27];  // "/proc/" + log_10(2**64) + "\0"
@@ -41,13 +46,24 @@ bool AdjustOOMScore(pid_t process, int score) {
     return false;
   }
 
-  const int fd = openat(dirfd, "oom_adj", O_WRONLY);
+  int fd = openat(dirfd, "oom_score_adj", O_WRONLY);
+  if (fd < 0) {
+    // We failed to open oom_score_adj, so let's try for the older
+    // oom_adj file instead.
+    fd = openat(dirfd, "oom_adj", O_WRONLY);
+    if (fd < 0) {
+      // Nope, that doesn't work either.
+      return false;
+    } else {
+      // If we're using the old oom_adj file, the allowed range is now
+      // [0, kMaxOldOomScore], so we scale the score.  This may result in some
+      // aliasing of values, of course.
+      score = score * kMaxOldOomScore / kMaxOomScore;
+    }
+  }
   close(dirfd);
 
-  if (fd < 0)
-    return false;
-
-  char buf[3];  // 0 <= |score| <= 15;
+  char buf[11];  // 0 <= |score| <= kMaxOomScore; using log_10(2**32) + 1 size
   snprintf(buf, sizeof(buf), "%d", score);
   size_t len = strlen(buf);
 
diff --git a/sandbox/linux/suid/sandbox.c b/sandbox/linux/suid/sandbox.c
index 1cf95284..a545208 100644
--- a/sandbox/linux/suid/sandbox.c
+++ b/sandbox/linux/suid/sandbox.c
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -37,6 +37,7 @@
 #define CLONE_NEWNET 0x40000000
 #endif
 
+static const char kAdjustOOMScoreSwitch[] = "--adjust-oom-score";
 static const char kSandboxDescriptorEnvironmentVarName[] = "SBX_D";
 static const char kSandboxHelperPidEnvironmentVarName[] = "SBX_HELPER_PID";