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

sandbox/linux/suid/process_util_linux.c

Index: sandbox/linux/suid/process_util_linux.c
diff --git a/sandbox/linux/suid/process_util_linux.c b/sandbox/linux/suid/process_util_linux.c
index 17453def621006ca2d824c45c21cb922d6849d60..31886e285cf4dac44398418703deddafcb96e470 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.
 
@@ -20,7 +20,7 @@
 #include <unistd.h>
 
 bool AdjustOOMScore(pid_t process, int score) {
-  if (score < 0 || score > 15)
+  if (score < 0 || score > 1000)

[stevenjb, 2011/08/18 00:20:07]

And in the darkness bind them?

[Greg Spencer (Chromium), 2011/08/18 23:10:50]

Also moved into a constant.

     return false;
 
   char oom_adj[27];  // "/proc/" + log_10(2**64) + "\0"
@@ -41,13 +41,24 @@ 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, 15], so we scale the score.  This may result in some
+      // aliasing of values, of course.
+      score = score * 15 / 1000;
+    }
+  }
   close(dirfd);
 
-  if (fd < 0)
-    return false;
-
-  char buf[3];  // 0 <= |score| <= 15;
+  char buf[5];  // 0 <= |score| <= 1000;

[stevenjb, 2011/08/18 00:20:07]

Maybe size this for any 32 bit range?

[Greg Spencer (Chromium), 2011/08/18 23:10:50]

Done.

   snprintf(buf, sizeof(buf), "%d", score);
   size_t len = strlen(buf);