svn commit: r258431 - head/sys/amd64/amd64

[Ed Maste]

Author: emaste
Date: Thu Nov 21 18:37:11 2013
New Revision: 258431
URL: http://svnweb.freebsd.org/changeset/base/258431

Log:
  Disable amd64 boot time memory test by default
  
  The page presence memory test takes a long time on large memory systems
  and has little value on contemporary amd64 hardware.
  
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/amd64/amd64/machdep.c

Modified: head/sys/amd64/amd64/machdep.c
==============================================================================
--- head/sys/amd64/amd64/machdep.c	Thu Nov 21 17:49:56 2013	(r258430)
+++ head/sys/amd64/amd64/machdep.c	Thu Nov 21 18:37:11 2013	(r258431)
@@ -1476,13 +1476,15 @@ getmemsize(caddr_t kmdp, u_int64_t first
 		Maxmem = atop(physmem_tunable);
 
 	/*
-	 * By default enable the memory test on real hardware, and disable
-	 * it if we appear to be running in a VM.  This avoids touching all
-	 * pages unnecessarily, which doesn't matter on real hardware but is
-	 * bad for shared VM hosts.  Use a general name so that
-	 * one could eventually do more with the code than just disable it.
+	 * The boot memory test is disabled by default, as it takes a
+	 * significant amount of time on large-memory systems, and is
+	 * unfriendly to virtual machines as it unnecessarily touches all
+	 * pages.
+	 *
+	 * A general name is used as the code may be extended to support
+	 * additional tests beyond the current "page present" test.
 	 */
-	memtest = (vm_guest > VM_GUEST_NO) ? 0 : 1;
+	memtest = 0;
 	TUNABLE_ULONG_FETCH("hw.memtest.tests", &memtest);
 
 	/*