Mercurial > hg > graal-jvmci-8

diff src/os/linux/vm/os_linux.cpp @ 12832:263f2c796d6c

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8024838: Significant slowdown due to transparent huge pages Summary: Don't turn on transparent huge pages (-XX:+UseTransparentHugePages) unless explicitly specified on the command line. This has the effect that large pages are never turned on Linux unless the user has explicitly enabled any of the large pages flags: -XX:+UseLargePages, -XX:+UseTransparentHugePages, -XX:+UseHugeTLBFS, and -XX:+UseSHM. Reviewed-by: jwilhelm, tschatzl, brutisso
author stefank
date Sat, 05 Oct 2013 10:14:58 +0200
parents 06ae47d9d088
children aa6f2ea19d8f
line wrap: on
line diff
--- a/src/os/linux/vm/os_linux.cpp	Thu Oct 03 21:36:29 2013 +0200
+++ b/src/os/linux/vm/os_linux.cpp	Sat Oct 05 10:14:58 2013 +0200
@@ -3361,13 +3361,15 @@
   if (FLAG_IS_DEFAULT(UseHugeTLBFS) &&
       FLAG_IS_DEFAULT(UseSHM) &&
       FLAG_IS_DEFAULT(UseTransparentHugePages)) {
-    // If UseLargePages is specified on the command line try all methods,
-    // if it's default, then try only UseTransparentHugePages.
-    if (FLAG_IS_DEFAULT(UseLargePages)) {
-      UseTransparentHugePages = true;
-    } else {
-      UseHugeTLBFS = UseTransparentHugePages = UseSHM = true;
-    }
+
+    // The type of large pages has not been specified by the user.
+
+    // Try UseHugeTLBFS and then UseSHM.
+    UseHugeTLBFS = UseSHM = true;
+
+    // Don't try UseTransparentHugePages since there are known
+    // performance issues with it turned on. This might change in the future.
+    UseTransparentHugePages = false;
   }
 
   if (UseTransparentHugePages) {
@@ -3393,9 +3395,19 @@
 }
 
 void os::large_page_init() {
-  if (!UseLargePages) {
+  if (!UseLargePages &&
+      !UseTransparentHugePages &&
+      !UseHugeTLBFS &&
+      !UseSHM) {
+    // Not using large pages.
+    return;
+  }
+
+  if (!FLAG_IS_DEFAULT(UseLargePages) && !UseLargePages) {
+    // The user explicitly turned off large pages.
+    // Ignore the rest of the large pages flags.
+    UseTransparentHugePages = false;
     UseHugeTLBFS = false;
-    UseTransparentHugePages = false;
     UseSHM = false;
     return;
   }